20 Dr. A. C. Stokes on some 



slightly divergent, its posterior termination on each' side 

 minutely acuminate; dorsal antenna a large deep pit sur- 

 rounded by a circular or broadly oval ring ; lateral antennae 

 apparently present as small capitate dorso-lateral projections, 

 but upon which I could discover no setai ; foot three-jointed 

 (or four-jointed if the prolongation of the body to which the 

 foot is a continuation be counted as a joint) ; toes long, 

 tapering ; eyes two, red, pectoral, crescentic, placed near the 

 frontal border, in some specimens the appearance of an addi- 

 tional pair of faintly coloured crescentic eye-spots not being 

 rare on the pectoral region ; flame-cells small, only one (near 

 the postero-lateral border) having been observed ; lateral 

 canals exceedingly numerous, especially in the dorsal region, 

 where they extend beneath the lorica in long loops and in 

 concentric curves, each canal terminating in a trumpet-shaped 

 mouth apparently not ciliated, an'l without an undulating 

 membrane, the vessels together imperfectly separable into 

 three groups, one central, two lateral ; contractile vesicle 

 large, ventrally and transversely placed near the anterior 

 extremity of the ventral sulcus and variously compressed and 

 changed in form by the pressure of the viscera. 



Length about t4^ inch ; length of lorica jyj ; toes and 

 foot ai^. 



The tigure (made with a camera lucida) was drawn from a 

 specimen under slight pressure/ and the head is therefore too 

 much rounded and too prominent. 



The frontal plate is movable and flexible. When the body 

 is contracted this plate is folded over the rounded part and 

 serves as a protection to the otherwise defenceless region. 



This seems to be the only known species with a stippled 

 band around the front border. This feature, together with 

 the lateral spinous processes, and especially with the numerous 

 canals of the vascular system, with their curves and their 

 trumpet-shaped mouths, makes the form one easily recog- 

 nizable. The Rotiferon frequently, I think usually, swims 

 on the back, thus concealing some important and interesting 

 structural features. 



Metopidia collaris^ var. similis, no v. 

 (PI. VII. fig. 5.) 



The foregoing species is so frequently accompanied or even 

 replaced by one or more varieties so distinct from it in the 

 form and the size of the lorica, that it merits varietal recog- 

 nition and a varietal name, as I have given it. 



The lorica is evenly oval in outline, depressed, the ventrum 



