DR. T. S. COBBOLD's SYNOPSIS Or THE DISTOMTDJE. 49 



Amphistoma Lari glauci, Rudolphi. 



Hab. Found by Bremserin Larus argentatus ; by Schilling in L. argen- 

 tatoides ; by Mehlis in L. tridactylus ; by Creplin in L. canus ; by 

 Natterer in L. marinus. It infests the intestines in all. 



8. Hemistoma excavatum, Diesing. 

 H. excavatum, Diesing. 



Distoma excavatum, Nitzsch, Mehlis, Nathusius, Dujardin. 

 Fasciola excavata, Rudolphi. 



Hab. Found by Rudolphi and Bremser in Ciconia alba ; by Nathusius 

 in C. nigra. 



Genus 16. Diplostoma (Diplosfomicm), Nordm. 

 Were it possible even with only a moderate degree of accuracy to refer 

 to their true adult representatives the several individuals here associated 

 together, I should be glad to cast aside this genus entirely ; but, while 

 accepting in a general sense the view of those who maintain that the Diplo- 

 stomes are merely larval or immature Holostomes, how, I ask, are we to 

 allocate under their proper specific titles even those forms which have been 

 most frequently subjected to investigation ? The differing views of Steen- 

 strup, Siebold, Aubert, Wagener, Claparede, and others, are at present 

 irreconcileable, and the difficulty is still further enhanced by the surprising 

 results of Leuckart's researches among the Pentastomata, where he finds 

 that even the presence of well-developed reproductive organs afl^ords no 

 safe criterion of the adult state, for, in these crustaceoid parasites they 

 exist in the pupa condition. As this obtains in the Pentastomes, may 

 not the evidence equally apply to the digenetic flukes ? Without at present 

 entering into the discussion, I think it advisable, if only for the sake of 

 convenience, to retain this genus imtil some one shall have more conclu- 

 sively established the affinities and alternating relations in the cycle of 

 development, as they affect, at least, a proportion of the so-called species. 



1. Diplostoma rhachi^eum, Henle. 



D. rhachicEwn, Henle, Dujardin, Leydig, Claparede. 



Tylodelphys rhachidis, Diesing, Revis. p. 12; Pagenstecher. 



Ent. dubium Ranarum, Rudolphi. 



Hab. Found by Henle, Caldani, Leydig, Claparede, Pagenstecher, and 



others, in the spinal canal of Rana iemporaria and Pelophylax escu- 



lentus. 



2. Diplostoma clavatum, Nordmann. 



D. clavatum, Nordmann, Gescheidt, Dujardin, Claparede. 

 Tylodelphys clavata, Diesing, Revis. p. 1 2. 



Hab. Found by Nordmann in the eyes of Perca fiuviatilis, Acerina vul- 

 garis, and Lucioperca Sandra ; by Dujardin in Esox Lucius. 



3. Diplostoma craniarium, Cobbold. 

 Tylodelphys ? craniaria, Diesing, Revis. p. 12. 



LINN. PROC. — ZOOLOGY, VOL, Y. 4 



