Hydroides inermis Monro, 1933b

(Figures 5, 12 A)

Hydroides inermis Monro, 1933b: 1083 –1085, Text-figure 27A–E. Type locality: James Bay, Santiago [James] Island, Galápagos, 9–11 m, on clean sand and weeds.

Hydroides inermis .—Bastida-Zavala & ten Hove 2003: 94–95, Figs 16A–K (Galápagos and Perú; 1–91 m); Salazar-Vallejo & Londoño-Mesa 2004: 54 (Tropical Eastern Pacific, checklist); Bastida-Zavala 2008: 27, fig. 6M (mentioned only); Bastida-Zavala 2009: 538, Fig. 2 K (identification key for Tropical America); ten Hove & Kupriyanova 2009: 53 (worldwide serpulid checklist).

Material examined. Three specimens.

Oaxaca: UMAR-Poly 771, 3 spec. (Agua Blanca Beach, rocks, intertidal, April 27, 2012, coll. OCR).

Habitat. Intertidal to subtidal (91 m, Bastida-Zavala & ten Hove 2003). In tide pools, on sand and weed (Monro 1933b; Bastida-Zavala & ten Hove 2003).

Distribution. Previously only known from the Galápagos Islands and North Perú (Bastida-Zavala & ten Hove 2003), our record extends its known geographical range from Santiago (James) Island, to Agua Blanca, Oaxaca (approximately 1,860 km to the north in a straight line).

Remarks. Some specimens of Hydroides inermis that have a more developed dorsal spine (Bastida-Zavala & ten Hove 2003, Fig. 16A) could be somewhat confused with H. brachyacantha or H. deleoni; however, H. inermis has fewer (7–8) and broad verticil spines, with blunt tips, while the two latter species generally have more verticil spines (7–11) with pointed tips. The species is rare except, maybe, in the Galápagos Islands (Bastida-Zavala & ten Hove 2003).