337] NORTH AMERICAS ASPIDOGASTRIDAESTUSKARD 57 



found no glandular structure in the fibrous part. Instead of supporting 

 I believe that they are subversive to the idea of the glandular nature of 

 th« organ. 



In my material the fibers which pass dorsad from the bulb are iden- 

 tical in appearance with the adjacent connective tissue and do not ap- 

 pear to be nervous. The muscular wall of the canal is I believe, used 

 primarily in the eversion and retraction of the external part of the canal. 

 In living specimens under observation the everted part of the marginal 

 organ was about the size and shape of the thick-walled distal portion of 

 the canal, and this is probably the only part protrusible. With tliis ever- 

 sion, the base of the thick walletl portion to which the nerve is distributed 

 would be at the tip of the everted structure in a position to function in a 

 sensory capacity. 



Comparisons. — This is the third aspidocotylean described from tur- 

 tles, the two previously reported forms being Cotylaspis Icnoiri Poirier 

 1886, and Lophotaspis vallci Stossieh 1899, both African species. Poirier 

 described C. Icnoiri from the intestine of Tctrathijra vaillanti from Sen- 

 egal, and Looss (1902) reports it as occurring also mTrionyx notiiica of 

 the Nile. Lophostaspis vallci is parasitic in the stomach of Thalassoclu li/s 

 corticata. Cotylaspis cokeri is very diffei'eut from Lophotaspis, but shows 

 considerable resemblance to C. Icnoiri. However, a comparison of the 

 description of C. Icnoiri with specimens of C. insignis and C. colcri shows 

 decided difference in the size and shape of the worms and of the adhesive 

 disc, in the number of alveoli and marginal organs, in the sive of ovary 

 and testis, of cirrus sac, and of eggs. The three forms agree in essential 

 morphological features and fit the diagnosis of the genus Cotylaspis as 

 given by Leidy, but are equally clearly good species in that genus. 



CL.VSSIFIC.VTION OF THE FAJIILT 



The last classification of tlie Aspidogastridae was made by N'ickerson 

 (1902). Since additions and changes have subsequently been made, 

 further revision seems advisable. The present arrangement is largely 

 based on the work of Nickerson and brings tlie classification to date. 

 Present information supports the validity of the following genera. 



I. Aspidogaster von Baer 1827. Type species, A. conchicola von 

 Baer. 



Oval adhesive disc, four rows of alveoli, marginal organs present, 

 mouth subterminal, no oral sucker, one testis. 



This genus contains A. conchicola which infests the pericardium and 

 renal organs of various species of Unionidae in Europe and Xorth Amer- 

 ica. It is also found in gastropods and in the immature condition in 

 th« intestine of Unionidae. Other species of this genus are A. limacoides 



