iKT. L'l. PARASITES OF SHARKS AND SKATES LINTON, 11 



Raja stabulifoHs. 



Collected in 5 of the years from 1904 to 1914, inclusive ; on 1 date 

 in April, 2 scoleces with short strobiles, about 5 mm. in length, and 

 numerous free proglottides; on 3 dates in May, 1 to 2 with numerous 

 free proglottides ; on 1 date in October, 1 . 



(U.S.N.M., Helm. Coll. 7664.) 



RHINEBOTHRIUM MACCALLUMI, new species. 



Plate 1. liirs. 2-A. 



Scolex with four, short-pedicelled bothria, which, when flattened, 

 are nearly elliptical, being slightl}^ narrowed at the anterior end 

 (fig. 3), each provided with about 16 pairs of loculi (fig. 4) ; neck 

 practically none. 



Strobile filiform, slightly swollen near the junction with the 

 scolex; segments begin near the scolex, at first as fine transverse 

 lines; first distinct segments much shorter than broad, increasing 

 in length gradually, becoming longer than broad; adult proglot- 

 tides not seen, last proglottides slender and rod-like with length 

 three times the breadth. 



Dimensions of specimen mounted in balsam (fig. 2) : Length 28; 

 bothrium, length 1.05, breadth 0.50; diameter, at junction of strobile 

 and scolex 0.18, at enlargement back of junction 0.21, at point 1 mm., 

 back of junction 0.16, at middle of length of strobile 0.18; distance 

 to first distinct segments 2.8; length of first distinct segment 0.02, 

 breadth 0.16; length of segments at middle of strobile 0.21, breadth 

 0.18; length of last segment 0.48, breadth 0.16; average length of 

 last 10 segments 0.40. 



Tliere were approximately 150 segments in the last 24 mm. of the 

 strobile. 



The bothria in one of the mounted specimens were flattened so as 

 to show the plan of loculi. In this specimen they were as shown 

 in figure 4, that is. 16 pairs, with an odd, terminal loculus at the 

 anterior end. 



Adult proglottides were not seen, but from the positions of rudi- 

 ments of cirrus-pouches, the genital apertures were seen to be irregu- 

 larly alternate, near the middle of the length of the proglottis, and 

 near the lateral margin. 



Type.—V.S.'^.ll.. Helm. Coll. 7665. 



Dasyhatis centriiro. 



1922, July 15 : 3, from spiral valve of a large sting ray. 



1923, August 20:3. 



