478 PROCEEDINGS OF THE NATIONAL MUSEUM vol.89 



Genus GNESIOCEROS Diesing, 1861 

 Pelagoplana Bock, 1913. 



Definition. — Planoceridae with oblanceolate pellucid bodies; with 

 tentacles containing eyes; with true seminal vesicle and interpolated 

 prostatic vesicle; cirrus armed with parallel toothed bands; vagina 

 with a powerful musculo-glandular fold; Lang's vesicle transverse. 



GNESIOCEROS FLORIDANA (Peaise, 1938), new combination 



Imogine oculifera VEatKiu., 1892, p. 475, pi. 40. fig. 1 (not /. ociiHfera Girard, 



1853). 

 Stylocfioplana floridana Pe-\kse, 1938, p. 77, tig. 27. — Pearse and Littler, 1938, 



pi. 20, fig. 5; pi. 22, figs. 14, 15, 17. 

 Stylochoplana oculifera Pearse and Walkek, 1939, p. 18, fig. 10. 

 Gvesioceros verrilli Htman, 1939a, p. 146, figs. 14-16. 



Material. — Many whole mounts and one set of serial sections in 

 Pearse collection, labeled /Stylochoplana floridana, including type. 



Form. — Oblanceolate, anteriorly expanded, tapering to a pointed 

 posterior end (see Hyman, 1939a, fig. 14, p. 145; also Pearse and 

 Littler, 1938, pi. 20, fig. 5); small, 6-8 mm. long; with a pair of 

 elongate, pointed tentacles. 



Eyes. — Each tentacle contains 4-10 eyes; loose cerebral groups of 

 8-20 eyes each lie between the tentacles extending before and behind 

 their level. 



Color. — Translucent greenish. 



Digestive tract. — Pharynx elongate, central, with moderate ruiiles; 

 intestinal branches greatly anastomosed, forming a reticulum with 

 rounded meshes. 



Reproductive system. — Fully described and figured in Hyman, 

 1939a, figs. 15, 16. Pera-se's figure and description (1938, p. 77, fig. 

 27) contain errors; the uteri are not confluent anterior to the pharynx; 

 Lang's vesicle is transversely crescentic, not globular. It is correctly 

 shown in Pearse and Littler, fig. 14, pi. 22, where, however, it is 

 labeled seminal receptacle, and the prostate is labeled efferent duct. 

 The cirrus is figured by Pearse and Littler, fig. 15, pi. 22, but I am 

 unable to understand the long strands shown coursing through the 

 cirrus. I have never in many specimens studied seen any such struc- 

 tures. In Pearse and Littler's fig. 17, pi. 22, the prostate is called 

 penis and the seminal vesicle is called prostate. Their sagittal sec- 

 tion, fig. 21, pi. 23, is in error in that a common genital pore is 

 indicated ; the species has separate genital pores. 



The genus Gnesioceros has a cirrus composed of parallel toothed 

 bands eversible to the exterior. There is an elongated cylindrical 

 prostate made of a succession of transverse chambers and enclosed 

 in the same muscular sheath as the cirrus. The thick musculoglan- 



