new and Uttle-known Trematodes. 519 



Zeugorchin acanthus, pen. ct s]). ii. 

 (PI. Xil. figs. 4, 5; PI. Xm. li-s. 0, 7.) 



From the bursa fabricii and cloaca of tlio licrring-gull 

 {Lariis arjjentatus) . 



Tlie body is of a somewhat oval outline ; flattened ven- 

 trally, convex dorsally. It is divided into three portions. 

 The anterior, corresponding to the head, bears the oral sucker, 

 surrounded by a collar carrying a row of spines. It is 

 separated from the rest of the body by a distinct though not 

 deep constriction. The breadth at the collar is '87 mm. 

 The middle |)ortion of the body is flattened and expanded, 

 with a breadth of 1"60 mm. In the posterior portion the 

 breadth reaches a maximum of 2'11 mm., from which point 

 it diminishes rapidly to the end. The posterior end is blunt. 

 The length of the whole animal is 3'91 mm., of wdiich the 

 posterior part comprises 2*4:3 mm., or nearly two thirds. 



The cuticle is beset with numerous rows of stout spines 

 (PI. XII. flg. 5). These cover the whole of the middle 

 portion of the body and part of the posterior. They are 

 almost entirely absent from the posterior half. The spines 

 vary considerably in size, those in front measuring '019 mm., 

 while those further back attain a length of '03 1 mm. The 

 rows are about '025 mm. apart anteriorly, but become more 

 widely separated on jiassing backwards. 



The ridge bearing the cephalic s[)inesis somewhat peculiar. 

 It bears a distinct resemblance to the collar of a coat, and 

 differs greatly from the corresponding structure found in the 

 genus Echinostovmm. It is flat, with very definite outline, 

 and its edges are carried right up to the oral sucker, so that 

 the terminal spines are contiguous with the rim of the sucker. 

 About 12 spines can be seen on each side in a ventral view, 

 while dorsally there are about 30, the total number being 

 about 60. They are all nearly equal in size (about '037 mm.), 

 but ventrally they appear to diminish somewhat as they 

 approach the end of the ridge, so that the spines nearest the 

 sucker are the smallest. The surface of the collar is slightly 

 furrowed by muscular bauds running down to meet the 

 spines. 



no ova. Ovar}- comparatively small aud vitt-lliue glandfl scant}'. Ceplmlic 

 suiiust 29 in number, reacliin^r a length of OUo mm. in some cases. Tl>e 

 lierrin"-gull from which the specimens were obtained was much infectea 

 witli parasites, I'ucotreina tinyiutuJid Levi)iseiiia simi/is occnir'ni'^ in great 

 numbers. Each parasite was conlinod to aparticuUir part of tlie gut, tlio 

 order being Echinostomum, Tocotrcma, LcLinscnia. 



