400 Zoological N. Y. Zoological Society. [I;20 



which owing to a few characteristics not possessed by other 

 members of this family, must necessarily make it constitute a 

 new species. It is small, being only 1 mm. in length by .10 mm. 

 in width ; it has, however, the usual general conformation of the 

 genus. 



Its body is elongated and narrow and of almost an equal 

 width throughout, except at the posterior end where the hook 

 disc is somewhat wider. The disc is, however, quite different 

 from any of the forms hitherto described ; it is more footlike in 

 shape, — in fact, in some specimens it is quite the shape of a foot, 

 but ordinarily it extends equally on each side of the end of the 

 body. This shape is caused largely by there being on each side 

 a prolongation of skin, which is armed with two small hooks. 

 Then on each side of the notch in the centre of the distal margin 

 there is fixed another small hook. In the centre of the disc to- 

 wards its margin are two small blocks of yellow chitinous tissue, 

 which give attachment to the bases of the main hooks of the 

 disc, of which there are, as usual, four — two attached to the 

 block placed in the anterior wall of the disc and two attached to 

 the posterior block. 



These blocks are of a peculiar shape and differ in each spe- 

 cies (Fig. 133). The blocks are each separated into parts which 

 like joints allow of the motion of the hooks at the will of the 

 worm. As will be seen also if observed closely, the hooks are 

 not of the same shape as those of other members of the genus. 

 In the posterior region may be seen the muscular bands which 

 extend from the disc up into the body and which control the 

 movements of the disc with its hooks. Some bands, if not the 

 chief ones, are seen to pass from one side of the disc to the oppo- 

 site side of the body. This is probably for the more varied ad- 

 justment of the hook disc. 



The head in its general conformation and the organs of the 

 body generally are much the same as in the description given 

 of the type except in the cases of the cirrus which is quite dif- 

 ferent and will constitute one decided point in the diagnosis of 

 the species. 



The male genitalia are the single large roundish testicle, 

 which lies posterior to the ovary in the center of the body. It 

 gives off from its anterior part the vas deferens which runs 



