60 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



pouch was from 0.45 to 0.56 mm. and the maximum diameter 0.15. 

 Its walls are strong, with spirally arranged muscles. The inner 

 portion incloses portions of the vas deferens (fig. 191). In sections 

 of ripe proglottides the cirri were missing, as if lost in the act of 

 copulation. In sections of adult unripe proglottides the cirri were 

 retracted. So far as they could be made out they seem to have 

 rather collapsible walls and are densely covered with minute spines 

 0.012 to 0.015 mm. in length. In a proglottis 1.33 mm. in breadth, 

 the length of the cirrus-pouch was 0.53, length of the cirrus 0.24. 

 The cirrus-pouch passes between the two lateral excretory vessels. 

 The vitelline gland lies on the median line near the posterior edge 

 of the proglottis. In a frontal section of a proglottis 0.28 mm. in 

 length and 0.84 in breadth, the vitelline gland was 0.045 in length and 

 0.12 in breadth. In a transverse section of a proglottis 1.08 in 

 breadth the thickness of the vitelline gland was 0.075, the breadth 

 0.14. The gland is compact, with short, blunt lobes. The ovary lies 

 anterior to the vitelline gland, and in adult proglottides its breadth 

 is approximately one-third that of the proglottis. A small empty 

 space dorsal to the vitelline gland was interpreted to be the seminal 

 receptacle. No trace of vagina Avas seen in any of the sections. The 

 number of testes was not determined. They are few and small and 

 medially situated, dorsal to the ovary, and, together with the vas 

 deferens, posterior to the inner end of the cirrus-pouch. 



The excretory vessels in each lateral pair lie close together; the 

 ventral is only a little larger than the dorsal, and there is a trans- 

 verse vessel at the posterior end of the proglottis connecting the 

 two ventral vessels. 



There are two layers of longitudinal muscles, each layer contain- 

 ing a large number of muscle bundles, 80, more or less, in the outer 

 layer, and a somewhat smaller number in the inner. The size of 

 the bundles is variable in each layer, but there is not much differ- 

 ence between the average size of the bundles of the two layers. The 

 bundles are subcircular in cross-section; individual fibers coarse. 

 There is a layer of circular fibers between the outer layer and the 

 subcuticla, and another on the inner side of the inner layer. The 

 medullary space is crossed by numerous strong dorso-ventral fibers. 



Record of collection. 

 Crocethia alba; 



1902, August 15. — Two scoleces and one strobile 24 mm. in 

 length; rostellum without hooks; breadth at posterior end 

 3.25 mm. The bird was obtained by Dr. John D. Milligan of 

 the Bureau of Fisheries steamer. Fish Hawk, near Cape Look- 

 out, N. C. 



(U.S.N.M., Helm. Coll. 7892 (type).) 



