Hood — On the Rotifera of the County Mayo. 



675 



I 



Ploesoma lenticulare — continued. 



ness by Mr. Dixon-Nuttall, Mr. "Western, and especially by Mr. 

 Rousselet bimself, has been to convince us that our species is not 

 identical with Ehrenberg's, that ^Vierzejski and Zacharias were 

 wrong in so associating it, and that accordingly Herrick's name 

 Ploesoma lenticulare must be reinstated in specific as well as in 

 generic priority. 



Description. — A complicated lorica almost completely encloses 

 the body. Viewed from the dorsal aspect it presents an elongated 

 anterior plate or neck-shield (a) whose lateral borders are free, 

 and to a slight extent overlap the adjacent portions of the lorica. 

 This neck-shield is traversed by a median longitudinal ridge, and 

 terminates in front in a prominent median tooth, with two angular 

 prominences on each side. A small specialised area at the 



Fig. 1. Fig. 2. 



posterior end of the neck-shield lodges the dorsal antenna, and 

 immediately behind this the lorica is crossed (in the middle of its 

 length) by two deep V-shaped transverse dorsal furrows. Posterior 

 to these transverse furrows, an elongated flattened triangular area 

 {a) extends backwards, and two long grooves {hh) converging 

 backwards from its sides meet together behind it, and run a narrow- 

 ing course to an apex at the posterior end of the lorica. The ridge 

 separating those two long grooves is thus a prolongation of the 

 apex of the triangular shield and the grooves themselves may be 

 defined as the " median vertical grooves." The rest of the lorica 

 consists of two lateral portions united ventrally to one another 

 from a point a little way behind the foot. They are separate from 

 one another anteriorly to this point, and are also separate from and 



