824 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [106] 



tion, which bears at each of its extremities a short, straightish hook. 

 The posterior loculus is long-elliptical with irregular borders. The an- 

 terior loculas is nearly circular, with thick and nearly entire borders. 

 The tissue of the sides and bottoms of these loculi is dense and firm. 

 The neck immediately behind the scolex is slender, short, and cylin- 

 drical. It expands abruptly into a large, lobed, crisped, and folded 

 mass, which, in alcoholic specimens, is more or less globose, but in liv- 

 ing specimens may spread out into a flat, suctorial organ with fimbri- 

 ated edges. This organ is so conspicuous and takes the place of bothria 

 so effectually, particularly as the scolex appears to be missing in the 

 larger specimens, that it may be called, with some degree of propriety, 

 the pseudoscolex. The ratio of the diameter of the pseudoscolex to the 

 true scolex may be from five to one, in young specimens, to thirty or 

 more to one in adult specimens. 



Behind the pseudoscolex the body is slightly flattened and longitud- 

 inally rugose. The unsegmented portion of the body is long, the seg- 

 ments appearing at first as transverse wrinkles, subsequently the seg- 

 ments decrease slightly in breadth and increase slowly in length. 

 Near the posterior end they become squarish and at the extreme pos- 

 terior end two or three times as long as broad. The ripe proglottides 

 are easily detached and continue active for a long time after removal 

 from the host. 



Genital apertures marginal, approximate, cirrus long. 



Length of strobile as much as one meter ; breadth of pseudoscolex 

 up to 15 n,m ; free proglottides as much as 8 mm long and 4.5 mm broad. 



Habitat — Tiger shark (Galeocerdo tigrinus), adult, half-grown, and 

 young specimens together in spiral valve, July 23, 1885, Wood's Holl, 

 Massachusetts. 



Family IV. TETRARHYNCHID^E. 



Subtribe Trypanorhyncha Diesing. 

 Subfamily Phyllorhynchince Van Benedcn. 



Subfamily I. Dibothriorhynchin^e. 



Family Dibothriorhynchidcc Dies. 



Khynchobothrium Eudolphi. 



Tetrarhynchu8 of authors. 



Body taeniaeform. Neck tubular. Head continuous with neck, with 

 two opposite bothria, parallel or converging at the apices, lateral or 

 marginal, entire or undivided, or, either bilocular with a longitudinal 

 partition, or bilobed or divided. Proboscides four, terminal, filiform, 

 armed, retractile in the neck, for the most part longer than the head. 

 Genital apertures, male marginal, female lateral, or male and female 

 marginal approximate. 



