82 The Molluscan Family Planorhidae 



small papilla and the sperm canal has a central outlet (fig. 3). The walls 

 of the vergic sac are thin but those of the preputium are rather thick. 



Female Organs. The spermatheca (S) is pear-shaped and less than 

 1 mm. long. The spemiathecal duct is longer than the spermatheca, very 

 narrow, and enters the short vagina (VG) near the female opening. The 

 uterus (U) is narrow and slightly longer than the spermatheca and its duct. 

 The nidamental gland (NG.) is long and narrow (about 3 mm. long) and 

 of larger diameter than the uterus. The oviduct (OD) is about 2 mm. long 

 and smaller in diameter than the nidamental gland but much wider than 

 the sperm duct. The albumen gland is short, somewhat pear-shaped with 

 large gland cells (fig. 6). It lies over the intestine, one loop of which 

 passes through a trough-like space on the under side of the albumen gland. 

 The junction between the oviduct, sperm duct, and ovisperm duct, together 

 with the albumen gland connections, are shown in figs. 7 and 8. 



Hermaphrodite Organs. The ovotestis (OT) consists of many club- 

 shaped diverticula placed in a double row. The ovisperm duct is very short 

 between the seminal vesicle and ovotestis but three times this length be- 

 tween the seminal vesicle and the oviduct. The duct is a narrow tube. 



Two other species of Tropicorbis have been dissected by the writer. 

 Tropicorbis nisei (Dunkerl (plate 13, fig. 9) has twenty-four diverticula on 

 the prostate and Tropicorbis obstructus (]\Iorelet) has eighteen diverticula 

 on its i)rostate. The penial complex is about the same in the three species. 

 Some of the diverticula of the prostate are folded over at the end in riisei 

 (figs. 4, 5). The retractor muscle complex is complicated in riisei but quite 

 simple in obstructus. The spermatheca is rounder and less pyriform in 

 riisei and obstructus and the ducts are longer than in havanensis (compare 

 the figures). In obstructus a number of the diverticula of the ovotestis 

 contained eggs almost ready to be discharged (plate 13, fig. 3). The junc- 

 tion of the prostate duct and the sperm duct to form the vas deferens is 

 shown in fig. 8 iriisei). 



Pilsbry (1934, p. 53) has figured the genitalia of Tropicorbis pallidus 

 (C. B. Adams), from Bolivar, near Santa Alarta, Colombia. This figure 

 differs in a few respects from the genitalia of riisei, havanensis and 

 obstructus as figured in this volume. There are twelve long and somewhat 

 irregular diverticula on the prostate. The penial complex shows a very 

 long and narrow vergic sac, considerably longer than the preputium. The 

 verge appears as in the other species studied. There is one retractor muscle 

 as in obstructus. 



It is evident from the knowledge afforded by the four species of which 

 the anatomy is known that there is considerable variation in the details 

 of structure of the genus Tropicorbis. The prostate, particularly, may bear 

 as many as fifty diverticula {havanensis) or as few as twelve diverticula 

 (paUidu.s) . The penial complex may have the vergic sac shorter than the 

 preputium {havanensis) or much longer than the preputium {pallidus). 

 There is complete agreement, however, in the long, narrow verge with 

 tenninal oj^ening, the lobulate seminal vesicle, the long and narrow oviduct, 

 nidamental gland, and sperm duct, and the rounded or pear-shaped 

 spermatheca on a long duct. It is desirable that the genitalia of the type 

 species {orbicidus = liebmanni) be known. It is believed to be like havan- 

 ensis, a related species. Hundreds of shells of orbiculus have been seen 

 but no material containing the animal has been available. 



