26 Dr. A. C. Stokes on some 



from the few glimpses which I have had of the dorsal aspect 

 the gastric gland seems to be single, narrow, and to extend 

 obliquely across the frontal region of the stomach ; but of 

 this there is no certainty, as momentary glances were all that 

 I could obtain, the body always slipping over to its side. The 

 animal's unrestrained movements are rotatory on its longi- 

 tudinal axis. 



Notommata mirabilis, sp. n. (PI. VIII. tigs. 20 and 21.) 



Body very soft and versatile ; in dorsal view broadly ovate, 

 posteriorly prolonged into a foot-like portion ; dorsum 

 rounded ; ventrum flattened ; front evenly and broadly convex, 

 and entirely without cilia, which are confined to an anterior 

 obovate space on the ventral surface ; auricles small, sub- 

 hemispherical, rarely protruded; lateral borders of the body 

 projecting on each side beyond the elevated and rounded 

 dorsal region as a flattened cuticular extension ; posterior 

 region narrowed and prolonged ventrally into two broad 

 conical toes, and dorsally into a narrow irregularly cylindrical 

 tail, which is shorter and smaller than the toes and habitually 

 held almost perpendicularly, so that when the animal is seen 

 in dorsal aspect this appendage appears in optical section like 

 a small ring or an elongated papilla, but in lateral view is seen 

 to be attached to the body by a minute peduncle, above which 

 it is subglobosely inflated, tapering thence with convex 

 borders to the subacute apex ; sense-organs (antennaj or 

 tentacles) four in number — one a small densely setigerous 

 pimple on each side of the convex front, and one a rather 

 more conspicuous seta-bearing papilla on each lateral border 

 of the dorsum, somewhat posterior to the transverse median 

 line ; brain large, not lobed, translucent, with one or more 

 posterior collections of opaque granules and with a dark, 

 almost black, posterior eye-spot ; contractile vesicle posterior, 

 in the median line, large, and, when fully expanded, about 

 one third as long as the body. 



Length from y|^o to y^y inch. 



The somewhat tripodal combination of foot and tail bears 

 considerable resemblance to those parts in Notommata tripus^ 

 Ehr., and in Notommata pilarius, Gosse ; but the species is 

 readily separated from both not only by the less robust 

 character of the tail, by its form and its perpendicular position, 

 but by the exceedingly peculiar and characteristic, not to say 

 unique, sense-organs, which at once distinguish it from all 

 known forms of the genus, and place it within not distant 



