no. 3631 BRANCHIOBDELLIDA — HOLT 3 



as to the generic unity of his Japanese worms. The correct name of 

 the genus, then, must be Cirrodrilus Pierantoni, 1905, and not 

 Stephanodrilus Pierantoni, 1906. If Goodnight was correct in placing 

 his species from Fall River, Calif., in the Asiatic genus, its name must 

 become Cirrodrilus obscurus (Goodnight). One of the conclusions of 

 the present paper, however, is that he was not correct and that S. 

 obscurus must become the type of a new genus. 



Magmatodrilus, new genus 8 



Stephanodrilus. — Goodnight, 1940, p. 55. [In part.} 



Type-species. — Magmatodrilus obscurus (Goodnight, 1940), here 

 designated by monotypy. 



Diagnosis. — Medium sized, stout branchiobdellid worms with two 

 pairs of testes; unpaired nephridiopore on the dorsum of segment in; 

 body terete; spermiducal gland with vasa deferentia entering entally; 

 prostate absent; ejaculatory duct present; bursa large, enclosing 

 protrusible penis entally; spermatheca present, not bifid, with ectal 

 duct and bulb invested with thick muscular covering. 



Distribution and affinities. — Magmatodrilus at this time stands 

 as a monotypic genus known only from the type-locality of M. 

 obscurus. 



Goodnight's (1940, p. 55) assignment of S. obscurus to Stephano- 

 drilus (= Cirrodrilus) appears to rest upon the absence of a prostate 

 and a mistaken belief that the anterior nephridia open by separate 

 pores on the dorsum of segment in. In addition to Cirrodrilus, the 

 genera Xironodrilus, Xironogiton, Ankyrodrilus, and Branchiobdella 

 have paired nephridiopores, lack a prostate and, with the exception 

 of Xironodrilus, the vasa deferentia enter the spermiducal gland 

 along its midlength rather than entally. Most genera that have a 

 common anterior nephridiopore also have a prostate gland. The 

 closest relatives of Magmatodrilus, then, should be among those 

 genera in which a prostate is absent and the anterior nephridia 

 open by a common pore on the dorsum of segment in. There are 

 three (possibly four) such genera, including an unnamed one repre- 

 sented by species from the southeastern United States and Mexico: 

 Bdellodrilus, Caridinophila, and the Mexican genus. The prostate 

 of Ceratodrilus (the fourth possible relative of Magmatodrilus) is a 

 minute lobe or region of differentiated epithelial cells on the side of 

 the spermiducal gland (Holt, 1960, pp. 57, 63). Leaving this question 

 for the moment, Bdellodrilus illuminatus (the genus is monotypic) 

 differs from Magmatodrilus in the possession of an eversible penis, 

 in the entrance of the vasa deferentia along the midlength of the 



3 From magma (Greek, =lava) + drilos (Greek, =worm), masculine, "lava- 

 worm" for the locality, springs in the lava beds of Shasta County, Calif., from 

 which topotypes were taken. 



