22 PROCEEDi:^GS OF THE NATIONAL MUSEUM. vol.64. 



of the remainder of the bothrium is thickened into a musciihir 

 sucker. While the shape of a bothrium at rest is circular, it as- 

 sumes many shapes while actively contractile, becoming elongated, 

 sometimes rather pointed in front, and, occasionally, there is a 

 slight protuberance at the posterior edge. The scolex, with the 

 exception of that part of the bothria which is enclosed by the larger 

 sucker, is translucent, as is also the very short neck-like portion. 

 The whole strobile is thickish, actively contractile, with a tendency 

 to coil in a spiral. No ripe segments were observed. 



Much confusion exists in the classification of the small cestodes 

 belonging to the Phyllobothriidae largely on account of the great 

 diversity of shapes which their soft and exceedingly contractile 

 scoleces can assume. It is desirable that extensive collections be 

 made from a large number of species of sharks and rays, and pre- 

 pared, as far as possible, under the same conditions, and by the 

 same technic. 



ORYGMATOBOTHRIUM PAULUM Linton. 



Plate 2, figs. 11-13. 



18970, p. 444, pi. 33, figs. 7, 8. 

 1901, p. 426. 

 1911, p. 586. 



Monorygnia galeocerdonis MacCallum, Zoopatli., N. Y. Zoolog. Soc, vol. 1, 

 p. 237, fig. 122. 



Records of this cestode not before published : 



The maximum length of mounted specimens is 15 mm. The cirrus 

 is long and slender with a bulbous base, which is armed with short 

 spines. An interesting feature, observed in a number of these worms 

 is that, while the genital pores are irregularly alternate, there is a 

 tendency for many successive proglottides to have these pores on the 

 same lateral margin. For example, in the sj)ecimen from which 

 Figure 12 was made, the 10 posterior proglottides had the genital 

 pores on the left side, then 1 on the right side, preceded by 12 on the 

 left side. In another the last 14 pores were on the right side, pre- 

 ceded by 5 on the left side. In another, 9 on the right side were 

 preceded by 10 on the left side, and these by 6 on the right side. 



Gcdeocerdo arcticus. 



Collected in 5 of the years from 1905 to 1915. 



On 1 date in June, many, over 100, in spiral valve of a shark meas- 

 uring 325 centimeters. On 4 dates in August: (1) 225, in spiral 

 valve of a 150-centimeter shark, taken at Menemsha Biglit. The 

 small cestodes found in this shark were examined with care but no 

 other species except young Thysanoce/phalum thysanoce'plialwii was 

 found; (2) about 100, maximum length 12 mm., bothria active; stro- 



