Subfa/fnlies, Genera, and Subgenera — Recent and Fossil 115 



Shell (plate 79, figt;. 16-18). Small, iiltradextral, of few whorls, the body 

 whorl large and expanded, embracing the previous whorl; whorls rounded 

 or carinated; the right side with whorls sunken below the upper surface or 

 showing a wide, slightly concave depression. There are no barriers or 

 lamellae within the aperture. The embryonic shell is punctate. 



Animal. The body is long and narrow, rounded before and sharply 

 pointed behind. The tentacles are long and filiform, the eyes large and 

 conspicuous, placed at the inner base of the tentacles. There may be two 

 dark lines of color extending down the neck and top of the head. In some 

 species (as melleus Lutz, plate 78, figs. 1, 2) the body is not much pig- 

 mented, but in some others (as hoffmani F. C. Baker, plate 10, fig. 1) the 

 l)ody is dcei^ly jngmented with black. 



ANATOMICAL CHARACTERISTICS 

 PLATES 9, 10, 11 



GENITALIA. Male Organs (plate 9, fig. 2; plate 10, fig. 2; plate 11, 

 fig. 3, respectively anatinum, hoffmani, and lucidum) . Seminal vesicle (SV) 

 large, much elongated, swollen, two to three times the diameter of the 

 ovisperm duct, varying in length in the three species examined. It is about 

 half the length of the ovisperm duct region in hoffmani but only about a 

 third of this lengi:li in lucidum. Anatinum is much like hoffmani. The 

 prostate (PRS) varies greatly in the three species: in hoffmani it is 3.5 

 mm. long and is made up of twenty-three short, club-shaped, widely spaced 

 diverticula; in lucidum, there are but eight diverticula on a prostate about 

 1 nun. long; in anatinum, there are seven diverticula still more widely 

 sjiaced and the prostate is about 1 mm. long. All diverticula arise directly 

 from the sperm duct and are not on a separate duct as in Segmentina and 

 other members of the subfamily. 



The sperm duct (SPD) also varies in length, being 5 mm. in hoffmani, 

 2.3 mm. in lucidum and a little over 1 mm. in anatinum. These lengths do 

 not include the sperm duct portion under the prostate diverticula. The 

 vas deferens of the three species is always a long, narrow tube, varying in 

 length in the different species. 



The penial comi~)lex is much elongated in all species examined. In 

 hoffmani (plate 10, fig. 5) the preputium is elongated, cylindrical, and 

 about twice the diameter of the long and narrow vergic sac, which is 

 nearly twice the length of the preputium. In lucidum, the preputium is 

 about three times the diameter of the vergic sac, which is considerably 

 longer than the preputium (plate 11, fig. 4). In another specimen, the 

 preputium and the vergic sac were about equal in length (plate 11, fig. 51. 

 In anatinum (plate 9, fig. 1), the vergic sac is shorter than the preputium, 

 which forms a reversed cone, becoming smaller in diameter toward the 

 ui^i^er part. 



The flagella of the three species differ considerably. In hoffmani (plate 

 10, figs. 6, 7, 8), the flagcllum is very short and is bifid at the end; in 

 lucidum (plate 11, figs. 4, 5), the flagellum is very long (1 mm. or more) 

 and is not bifid at the end; in anatinum (plate 9, fig. 1), the flagellum is 

 as long as the preputium (0.6 mm.) and is bifid at the end. A strong 

 retractor muscle is attached to the end of the vergic sac near the 

 insertion of the flagellum (plate 10, fig. 7). There is also a large nerve 

 at this point (N). 



