AKT. 21. PABASITES OF SHARKS AND SKATES LINTON. 77 



RHYNCHOBOTHRIUM LONGISPINE Linton. 



Plate 12, figs. 110-114. 



1890, pp. 835-837, pi. 11, figs. 18-20 

 1901, p. 433. 

 1911, p. 588. 



Adult stage. 



Dasyhatis centrura. 



1903, September 1 : Many small Rhyncliobothria were present in 

 the chyle of the spiral valve ; a few of them separated from the lot 

 after they had been Ij'ing over night in formalin, were referred to 

 this species. 



Larval stage. 



The encysted stage referred provisionally to this species, and 

 found in various intermediate hosts is the same as that from Steno- 

 tomus cJuysops (18975, pi. 63, figs. 10-13). At the base of the pro- 

 boscis the hooks, for a short distance, are rather straighter than they 

 are elsewhere on the proboscis, and are somewhat appressed. They 

 then become longer and more divergent (figs. 110, 111, 113), dimin- 

 ishing towards the tip. In the basal and middle regions there is not 

 a great diversity in shape, the longer hooks being rather slender, 

 tapering and arcuate. Towards the tip the hooks on one side of the 

 proboscis are short, broad, and abruptly recurved, on the other side 

 of the proboscis the}^ are slender and arcuate (figs. 112, 114). Tliis 

 is in agreement with forms found in Centrojn-istes stHatus (18976, 

 p. 793; pi. 62, fig. 12). 



Leptocephalus conger. 



1903. August 24: Small oval cysts in intestine; doubtless recently 

 introduced with food; stomach contained partly digested scup. 



Microgadus tomcod. 



1910, July 13: 2 small cysts. Figui'es 110-112 shows views of 

 different regions of the proboscis of a laiwa from one of these cysts. 



(U.S.N.M., Helm. Coll. 7707.) 



Paralichthys dentatus (figs. 113, 114). 



Collected in 4 of the years from 1903 to 1910, inclusive : Small oval 

 cysts, on viscera, in mesentery, and in wall of stomach and intestine. 

 On 1 date in July, several small, oval cysts on mesentery, 1 fish ex- 

 amined; 4 dates in August, several cysts, on each date, on viscera 

 and in wall of stomach and rectum. 11 fish examined ; 1 date in Octo- 

 ber, several c}'sts in stomach wall. 



(U.S.N.M.,'Helm. Coll. 7718.) 



Prionotus carolinus. 



1905, July 17 : 1 cyst on viscera, 17 fish examined. 



