New species, misidentifications and problematic taxonomy of some Atlantic South American marine mollusks: a review Author Simone, Luiz Ricardo L. text Papéis Avulsos de Zoologia 2024 2024-08-09 64 1 104 https://doi.org/10.11606/1807-0205/2024.64.031 journal article 10.11606/1807-0205/2024.64.031 1807-0205 14705562 Genus Bathyarca Kobelt, 1891 Bathyarca arcadia new species ( Figs. 45 , 46 A-E) https://zoobank.org/ 6C0FC89C-AAE7-49CD-AB2D-E0622D676960 Types: Holotype MZSP 166512 , shell . Paratypes : MZSP 166514 , 20 shells, MNHN-IM-2000-39812, 3 shells from type locality. BRAZIL . Espírito Santo ; off ItaÚnas, 19°41′S 37°48′W , 790-940 m , MZSP 166516 , 40 shells, MNHN-IM-2000-39813, 20 shells ( R . V . Marión-Dufresne col., MD55 sta. CB77 , 27.v.1987 ) . Type locality: BRAZIL . Espírito Santo ; off ConceiÇão da Barra , 18°59′S 37°50′W , 637 m [ R . V . Marión-Dufresne col., MD55 sta. CB76 , 27.v.1987 ] . Diagnosis: SE Brazilian species with oblique outline, delicate outer sculpture. Hinge with very oblique teeth in both ends, middle teeth minute, narrow, deformed. Description: Shell of ~ 7 mm , rather oblique; length similar to height; maximum inflation ~80% of length ( Fig. 45C, M ). Color white ( Fig. 46 A-F) to pale beige ( Fig. 45 A-F),with hairy beige periostracum close to edges ( Figs. 45A, B, K , 58E ). Right valve slightly smaller than left valve, exceeding in ventral edge ( Fig. 45A, F, K ). Prodissoconch elliptic, smooth, simple, of almost 1 mm ( Fig. 45J : arrow). Umbones prominent, blunt, elevating ~6% shell height beyond hinge; separated from each other, locat- ed in anterior end of mid third of hinge. Lunule narrow, concave, ~10% of shell width, slightly broader anterior to umbones ( Fig. 45C, M ). Dorsal edge straight; anteri- or edge rounded, slightly smaller than posterior edge; ventral edge bluntly angular in its division with posteri- or edge. Sculpture delicate reticulated; radial cords predominating in right valve ( Figs. 45A, K , 46E ), ~45 radial cords from anterior to posterior hinge edges; commarginal cords predominating in left valve ( Figs. 45B, L , 46D ). Hinge with 3-4 middle teeth very minute, narrow, rather deformed, located lightly posterior to umbo; anterior to them from 5 ( Fig. 46C ) up to 8 ( Fig. 45 G-I) very oblique teeth, prosogire, average angulation ~45° in relation to antero-posterior shell axis, second and third teeth as largest ones; posterior to narrow teeth 6 ( Fig. 46C ) up to 8-9 ( Figs. 46 G-H, 59B) very oblique teeth, opisthogire, average angulation ~45° in relation to antero-posterior shell axis, penultimate tooth as largest. Inner surface white, opaque; muscle scars of difficult delimitation; scars of anterior and posterior adductor muscles round- ed, located below both hinge ends. Figure 45. Bathyarca arcadia shell of types:(A-J) holotype MZSP 166512 (W 7.6 mm); (A) right valve, outer view; (B) left valve,outer view; (C) whole dorsal view; (D) left valve,inner view;(E) right valve,inner view;(F) ventral-sightly right view;(G) left valve,detail of hinge;(H) same for right valve;(I) semi-articulated hinge, ventral view,left valve up;(J)right valve,detail of umbo,left view,arrow showing prodissoconch;(K-M) paratype MZSP166814#1 (W 7.4mm),right,left and dorsal views.Scales:= 1 mm. Figure 46. Bathyarca arcadia and B.glomerula shells of types:(A-F) B. arcadia ; (A) paratype 166514#2 (W 6.9 mm),left valve,inner view;(B) same,detail of hinge, scale:= 1 mm; (C) paratype MZSP 166516#1 (W 5.0 mm),left view,inner view; (D) same,outer view;(E) paratype MZSP 166516#2 (W 5.0 mm),right valve,outer view;(F) same,inner view;(G-K) B. glomerula syntypes USNM 63166 (courtesy Ellen Strong);(G) #2 (W 5.6 mm),left valve,inner view;(H) same,outer view;(I) #1 (W 5.3 mm),left valve,inner view;(J) #3(W 4.1 mm)m right valve,inner view;(K) same,outer view. Etymology: The specific epithet is in apposition and a make-up word, although has a meaning in Latin of adventuresome, an allusion to difficulty in finding this isolated population. Distribution: Rio Grande do Norte ( Francisco, 2015 ) to Rio de Janeiro coasts.