TREMATODES 



179 



Fig. 290 



Cotylogaster 



occidentalis 



(Nickerson). 



References 



as in Fig. 288 



Fig. 291 



Cotulaspis 



msi(jni8 



(Osbbrn). 



References 



as in Fig. 288. 



3. CoTYLASPiS Leidy. Sucking disc broadly elliptical with 3 rows 

 of transversely elongated depressions; marginal sense organs and 2 eyes 

 present: in the mantle cavity of mussels and the intes- 

 tine of turtles; 2 species. 



C. insignis* Leidy (Fig. 291). Length 1.8 mm.; num- 

 ber of depressions about 29 : on the kidney 

 of Anodonta; common. 



4. AspiDOGASTER von Baer. Small 

 worms in which the body consists of a cyl- 

 indrical anterior portion and a veiy large 

 elliptical ventral disc in which are 4 longi- 

 tudinal rows of sucking depressions, num- 

 bering 64 to 120 and with marginal sense 

 organs ; 1 testis : in the intestines of fishes 

 and in fresh-water pelecypods and marine 

 gastropods; several species. 

 A. conchicola v. Br. (Fig. 292). Body elongate; number of depres- 

 sions about 64; length 3 mm.; 34 marginal sense organs: mostly in the 

 liver, pericardium, and kidney of Unio and Anodonta; Europe. 



Order 3. DIGENEA.f (Fig. 293.) 

 Entoparasitic, digenetic trematodes living in two or 

 more hosts, to which they attach themselves by means of 

 either one or two median 

 suckers. One of these is al- 

 ways an oral sucker and at 

 the front end of the body, ex- 

 cept in Bucephalus; the second 

 sucker, when present, is either 



on the ventral surface or at the hinder end 



of the body and is called the acetabulum. 



A few blood-infesting forms are without 



suckers. In the Holostomidae an additional 



organ of attachment in form of a large disc 



or projection back of the acetabulum is also 



present. Hooks are never present in con- 

 nection with the suckers but in some cases 



with the genital organs, and the body is 



often covered with small spines. The median 



Fig. 292 

 Aspidogaster 



conchicola 

 (Monticelli). 



References 

 as in Fig. 288, 



Fig. 293 — Diagram of a 

 digenetic trematode (Ben- 

 ham, altered). 1, oral suck- 

 er ; 2, brain ; 3, genital 

 pore ; 4, intestine ; 5, cir- 

 rus ; 6, receptaculum semi- 

 nis ; 7, acetabulum ; 8, ovary ; 

 9, excretory canal ; 10, Lau- 

 rer's canal ; 11, yolk glands ; 

 12, testis : ■ 13, excretory 

 pore ; 14, uterus. 



* See "On the Habits and Structure of Cotylaspis Insignis," etc., by H. L. 

 Osborn, Zool. Jahrb. Abt. f. Anat., Vol. 21, p. 201. 



t See "Synopsis of the Trematodes, Part II. The Aspidocotylea and the Mala- 

 cocotylea," etc., by II. S. Pratt, Am. Nat., Vol. .10, p. 887, 1902. 



