142 PROCEEDINGS OF THE NATIONAL MUSEUM vol. i04 



Family Prosthiostomidae Lang, 1884 



Genus Prosthiostomum Quatrefages, 1845 



Prosthiostomum pulchrum Bock, 1913 



Figures 88,6; 89,a 



Prosthiostomum pulchrum Bock, 1913, p. 285, text figs. 62, 63; pi. 5, fig. 10. 



Material: Five specimens from the Smithsonian-Hartford Expedi- 

 tion (Nos. 23,32, 66). 



Form: Typical of the genus, slender, elongated (fig. 88,6) ; of small 

 size, largest specimen 9 mm. long by about 1.5 mm. wide; type speci- 

 men was 12 mm. long. Bock's statement that the species is relatively 

 broad and short for the genus is not upheld by the specimens available 

 to me, which show the usual long slender shape. No doubt the single 

 specimen he had was contracted. 



Eyes: The rather large cerebral eyes form two wedge-shaped 

 groups, not well separated from each other, of about 40 eyes each, 

 in the larger specimens; the band of eyes along the anterior margin 

 contrasts with the cerebral eyes by the small size of its members 

 (fig. 88,6). The marginal band is also very short, not extending 

 beyond the anterior end of the cerebral groups. 



Color: Apparently a dirty tan Avith brown or black spots. The 

 spots are evident in some of the specimens. 



Digestive tract: Typical of the genus. 



CopuLATORY apparatus: The postpharyngeal part of one specimen 

 was sectioned sagittally and proved in good condition. A sagittal 

 view of the copulatory apparatuses is shown in figure 89,a. 



As Bock's specimen was imperfect in the male region and his figure 

 small and lacking in detail, it appears desu'able to give a figure here. 

 As found by Bock, the male and female gonopores and the large 

 sucker are close together. The male pore leads into a long antrum 

 slanting markedly forward; this has a rather thick muscular layer 

 outside the lining epithelium. At its anterior end it enlarges and 

 curves posteriorly, terminating with the penis. The penis papilla is 

 a small eminence bearing the penis stylet, which is surrounded distally 

 by the usual penis sheath. The male antrum is continued as a narrow 

 cavity around the penis papilla, and that portion of this cavity 

 traversed by the base of the penis stylet is provided, as usual in the 

 genus, with prostatic glands. Three ducts unite inside the penis 

 papilla — a larger ejaculatory duct, and two smaller ducts, one from 

 each of the accessory vesicles. The latter are, as usual in the genus, 



