Chondrobasis Arconada and Ramos, 2001

Arconada, B. & Ramos, M. A., 2001, New data on Hydrobiidae systematics: two new genera from the Iberian Peninsula, Journal of Natural History 35 (7), pp. 949-984 : 968-969

Chondrobasis Arconada and Ramos new genus

Type species Chondrobasis levantina n. sp.

Etymology

The name Chondrobasis derive from the greek `chondros ’ and `basis ’, referring to the wart or excrescence in the penial base.

Diagnosis

Shell. Depressed trochiform or valvatiform. External surface of the protoconch wrinkled, with marked punctum-like sculpture. The teleoconch is smooth with ®ne growth lines. Frontal aperture roundish with a slightly thickened columellar border that leaves a very narrow umbilicus. Thin outer lip. The peristome is slightly oblique and adapically sinuate.

Operculum. Corneus, thin, ovate, paucispiral with a submarginal nucleus. The internal callus is large and well developed.

Nervous system. The supraoesophagea l connective is quite long while the suboesophageal one is very short (®gure 4A). The pedal ganglia are linked to the cerebral and to the pleural ones by long connectives. The oesophagus runs straight along the cerebral ganglia.

Radula. Typically taeniaglossan. Trapezoidal central teeth with lateral wings that have one basal cusp on each side arising from the lateral margins. The central tooth has a squared basal tongue as long as the lateral margins and a long, wide and blunted central cusp with several small denticles on each side; the excavation of this tooth is more than 50% of tooth height. The upper border of the cutting edge of the central teeth is weakly excavated. The lateral tooth has a very long denticle (®gure 15E) and a rectangular face. The cusps of the inner marginal teeth are uniformly distributed, larger than those of the outer marginal teeth and usually fused in groups (®gure 15E, F).

Non-genital anatomy. The ctenidium is totally absent (®gure 4C). There is an osphradium of intermediate width located near the neck, very close to the inner border of the mantle cavity. Pallial tentacle absent. The cephalic tentacles are about eight times as long as wide, parallel-sided, and the distal end is not expanded. The eyelobe is weakly developed. The foot sole is unpigmented. The buccal mass is large relative to the snout. External caecum absent from the posterior chamber of the stomach which is slightly smaller than the anterior one (®gure 4E). The stomach has a single opening to the lobed digestive gland, which extends from the posterior chamber of the stomach to the end of the body. The rectum loop in the pallial cavity is open, U-shaped and leans to the prostate or to the pallial gland (®gure 4B). The anus is located very close to the anterior edge of the pallial cavity (®gure 3A, B). The faecal pellets are oval and yellowish. The intestine forms a U-shaped loop adhered to the wall of the style sac, which slightly protrudes (®gure 4E). The kidney is longitudinal and is located, between the prostate gland or pallial oviduct and the style sac, completely behind the pallial cavity (®gure 3B).

Female genital system. The ovary occupies more than 66% of the visceral coil posterior to the stomach (®gure 3B). It is a simple globular mass of vitellogenic oocytes, included in the ovarian follicles. The unpigmented renal oviduct generally forms an S-shaped loop, but sometimes it more closely resembles an open circular loop. The capsule gland constitutes approximately three-quarters of the pallial oviduct, leaving a small albumen gland. It is yellowish and frequently has black spots on its external epithelium. The bursa copulatrix clearly protrudes to the end of the pallial oviduct. It has no visible duct so the opening of the bursa is located close together to the anterior beginning of the renal oviduct. The RS1 is absent and the RS2 is pyriform-elongate d and always leans tightly on the oviduct but not over the bursa copulatrix. It is placed slightly posterior in the loop of the renal oviduct.

Male genital system. The testis has simple, stalked lobes that occupy more than 66% of the visceral coil which overlap anteriorly to the posterior chamber of the stomach (®gure 3A). The anterior coils of the seminal vesicle also overlap the stomach and enter the prostate gland in its middle zone (®gure 4D). The male genital ducts can be distinguished by the iridescent colour of the sperm. The large prostate gland extends to the pallial wall approximately one-half of its length and is typically bean-shaped (®gure 4D). The pallial vas deferens exits near its anterior end. The penis is inserted in the middle right part of the head, behind the base of the right tentacle. It is unpigmented, cylindrical in transverse section, elongated and gradually tapered towards the tip. The slender distal part of the penis is markedly diOEerent in shape from the wider basal part. There is a small, non-glandular papilla located in the concave side of the penis base. The penis duct strongly coils at the base of the penis.