50 CEYLON PEARL OYSTER REPORT. 



whilst anteriorly the centre bears usually a slight papilla with rings round it ; the 

 distinctness and size of this latter varies, however, greatly with the state of 

 contraction of the specimen (Plate, fig. 2). In some specimens the head was swollen, 

 and then its longitudinal diameter equalled its greatest transverse diameter, but, as a 

 rule, the transverse axis is three times the length of the antero-posterior. There is no 

 armature. Also there is no neck, the strobilization commencing immediately behind 

 the head. The proglottides are at first many times as broad as long, but these 

 proportions alter as we pass backward, and at the posterior end of the body they are 

 perhaps one and a half times as long as they are broad. Each proglottis has a very 

 well marked salient posterior border, and their shape and relative size at different 

 regions of the body are well shown in fig. 1. Altogether there are about 100 

 proglottides, and the whole tapeworm measures on an average 1 "5 centims. in length, 

 and about 0"5 millim. to 07 millim. in breadth where it is broadest. These tape- 

 worms were, when preserved in formalin, stout and stiff, with well cut outlines. 



In transverse sections the proglottides are circular, and the genital pore opens for, 

 at any rate, some consecutive proglottides on the same side, if one may speak of the 

 side of a cylindrical body. It was not possible to make out details of the sexual 

 organs beyond this fact, and that the uterus in the posterior proglottides is follicular. 



As it has been impossible to find any figures or descriptions which correspond at all 

 closely with this animal, we have ventured to establish a new genus which we 

 propose to call Staurobothrium, and since it is found in the Bird Ray, I suggest the 

 specific name of cetiobatidis. The name Staurocephalus would better have fitted the 

 facts, but unfortunately it has been used before. 



The formal definition is as follows : 



Staurobothrium, n. gen. 



Cestode with large cruciform head, without hooks, genital pore lateral, no neck. 



Staurobothrium cetiobatidis, n. sp. Head without hooks or any armature, it consists 

 of four well marked arms projecting from a centre, like the arms of a Maltese cross ; 

 each arm ends in a shallow sucker ; anteriorly where the arms meet is a low annulated 

 papilla representing the rostrum, but, as said above, there are no hooks. There is no 

 neck. Each proglottis overhangs the one which succeeds it by salient angles forming 

 a funnel-shaped skirt. The genital opening is on one side. The uterus, when full of 

 ova, is follicular. The average length of the worm, with about 100 proglottides, is 

 15 millims., the average width from 0*5 millim. to 07 millim. 



The systematic position of this Cestode is obscure. In structure the head super- 

 ficially resembles that of Ci/lindrojiJiorus, Dies., but it bears no hooks. Very little 

 change would be required in the architecture of the head to turn Staurobothrium 

 into the Calyptobothrium of Monticelli, but the terminal sucker of the latter is 

 absent in the new genus. In this respect it differs also from Linton's genus Crosso- 

 bothrium. On the whole I think we are justified in placing Staurobothrium in 



