4 PROCEEDINGS OF THE NATIONAL MUSEUM V0L - 1Z4 



spermiducal gland, and in the primitive bifid character of the sperma- 

 theca. Caridinophila unidens (another monotypic genus) from Yunnan 

 Province, China, lacks a spermatheca, has a peculiar almost spherical 

 spermiducal gland (Liang, 1963, pp. 564, 569), and cannot be con- 

 sidered in any way close to Magmatodrilus. The unnamed group 

 of species from Mexico, Georgia, and South Carolina resembles 

 Magmatodrilus in the absence of a prostate, in the entrance of the 

 vasa deferentia at the ental end of the spermiducal gland, and in 

 the large size of the copulatory bursa, but differs in the facies (size 

 and shape) of the jaws and most importantly in the presence of an 

 eversible penis instead of the protrusible one of M. obscurus. The 

 latter point requires further comment: the penes of Bdellodrilus 

 illuminatus, Ceratodrilus, Oedipodrilus, Branchiobdella, and perhaps 

 those of Cirrodrilus and Ankyrodrilus are eversible, i.e., the penis 

 itself is turned inside out in copulation; those of other genera are 

 protrusible, i.e., the bursal atrium everts and carries to the outside 

 a cone-shaped muscular penis papilla that does not itself evert. 

 Material in museum collections, however, rarely contains animals 

 with everted or protruded penes, and conclusions as to the func- 

 tioning of the organ frequently, as in the case of Magmatodrilus, 

 rest on inferences from the structure of the uneverted or unpro- 

 truded penis. In brief, Magmatodrilus also is related to Ceratodrilus 

 but differs in the lack of body ornamentation (peristomial and body 

 tentacles or projections), in the presence of a rudimentary or vestigial 

 prostate in Ceratodrilus, and in the presence of a protrusible instead 

 of an eversible penis in Magmatodrilus. Further study may unite the 

 species of the unnamed southeastern genus with Magmatodrilus, but 

 following the criteria previously used (e.g., Holt, 1953, 1960, 1965; 

 Hoffman, 1963; Liang, 1963), Magmatodrilus must be considered a 

 separate genus. 



Magmatodrilus obscurus (Goodnight) 



Figures 1-4 

 Stephanodrilus obscurus Goodnight, 1940, p. 55. 



Diagnosis. — Jaws subrectangular in en face view, dental formula 

 6/5; prosomites of segments i-iv, viii raised (supernumerary 

 muscles present); spermiducal gland with large anterior deferent 

 lobe, shorter posterior one, gland long and looped at ental end of 

 bursa; bursa large, extending to dorsal margin of segment vi; 

 spermathecal bulb clavate or bulbose, without ental process, wrinkled 

 and often appearing in sections to be diverticulate. Average size of 

 10 measured animals 2.8 mm in length. 



Type-locality. — Fall River, Shasta County, Calif. (Goodnight, 

 1940, p. 55). Additional topotypical material: Thousand Springs 



