BY JAS. P. HILL. 19 



appear to correspond to the fibres Spengel has observed in 

 Balanoqlossus canadensis and B. kupfferi, and which he regards 

 as having been carried in, by the infolding of the splanchnic 

 epithehum. 



Collar : Tlie epidermis of the collar can, like that of the other 

 species of Pti/chodera, he divided into five zones (fig. 15 [1-5]). 

 Of these the first formed l)y the anterior free rim of the collar is 

 the largest; the second occupies the region of the circular groove; 

 the third, that of the circular projecting cushion; the fourth, the 

 Ijottom of the typical ring furrow; while the fifth is formed by 

 tlie narrow projecting rim forming the posterior boundary of the 

 collar. The second and fourth zones are similarl}^ constituted; 

 they stain darkly with ha^matoxylin, and as in Ft. ininnta the}' 

 contain in their whole depth numerous gland cells; the remaining 

 zones contain gland cells only in their outer regions, and stain of 

 a lighter colour. 



Collar 7nusciLlature : It is in this species in its general relations 

 essentially similar to that of Pt. nunida. 



In the outer wall of the anterior part of the collar there is the 

 usual external layer of longitudinal muscle fibres (figs. 14, 16, Ifw.) 

 which spring in the posterior part of the collar between the 

 lonofitudinal muscle bundles of the inner wall. Internal to these 

 there is the layer of circular fibres which terminate at the 

 beginning of the second epidermal zone (figs. 14, 16, c/k'.). The 

 longitudinal muscles of the inner wall of the collar springing from 

 the region of the collar trunk-septum are, as in Pt. minitta, 

 separated in the posterior part of the collar into distinct bundles 

 by radial fibres passing between the outer and inner walls of the 

 collar. The ventro-lateral bundles terminate behind the circular 

 vessel fold of the collar, while those- more dorsally situated pass 

 towards the neck of the proboscis, and are inserted, as in Pt. 

 libinuta, mainly into the boundary membrane of the notochord 

 (fig. 16, il/n.; fig. 11, ccp.). The dorsal portion of the longitudinal 

 musculature extends, in the posterior region of the collar, round the 

 lateral surfaces of the perihi^mal spaces, and partly_on to the dorsal 



