108 P^ECILASMA CRASSA. 



Terga, minute, almost rudimentary, scarcely broader 

 than the carina, and half as long as the chord of its arc ; 

 carinal margin slightly curved ; scutal margin straight, 

 with a slight prominence fitting into a notch in the scuta ; 

 basal end bluntly pointed. 



Carina, (fig. 3, a) rather shorter than the scuta, 

 extending up only to the basal ends of the terga; 

 moderately curved ; apex moderately sharp ; middle part 

 broadest, externally carinated; internally not concave, 

 with the inner lamina of shell, at the basal end, pro- 

 duced into a very small oblong disc or tooth, which is 

 only as wide as the narrowest upper part of the valve. 

 The exterior keel does not extend on to this disc, which 

 is slightly constricted at its origin. 



Peduncle very short, narrow, ringed, and apparently 

 without spines. 



Size. — Capitulum four tenths of an inch long. 



The following parts of the animal are described from 

 some small and not well preserved specimens from 

 Madeira, which I owe to the kindness of Mr. Lowe. 



Mouth. — Labrum highly bullate in the upper part, 

 with large, inwardly pointed, unequal teeth. Mandibles, 

 with four large, pointed, equal- sized teeth, with the inferior 

 angle very narrow, acuminated like a single spine. 

 Maxillae, with three (?) large upper spines, of which the 

 middle one is extremely strong and long, beneath which, 

 there is a deep notch with a single strong spine, and 

 with the whole inferior part square and much upraised, 

 so as to stand on a level almost with the tips of the great 

 upper spines. 



Cirri in a miserable state of preservation ; first cirrus 

 short, second cirrus with rami unequal, and I suspect the 

 anterior one the longest ; some of the other cirri also 

 have unequal rami. The segments of the posterior 

 cirri are not protuberant, they have on their anterior 

 faces a single transverse row of bristles : in the upper 

 segments, some of the spines in each dorsal tuft (which 

 is much spread out), are much thicker, though rather 



