OXYNASPIS CELATA. 135 



radiating from their umbones ; hence their margins are 

 serrated with blunt teeth; their surfaces, moreover, are 

 sparingly studded with small calcareous points. 



Scuta (fig. 1, a), sub-triangular, with the lower part 

 rounded and protuberant, the upper produced and pointed. 

 The umbo is situated in the middle of the occludent 

 margin, instead of at the rostral angle, as in the foregoing 

 genera. The occludent margin is straight, and is bordered 

 by a narrow step or ledge, formed of transverse growth- 

 ridges, and therefore has its edge serrated : the rostral 

 angle is often slightly produced into a small projection. 

 The basal margin is short, and forms an angle above a 

 rectangle with the occludent margin : the tergal margin 

 is straight ; the carinal margin is rounded, protuberant, 

 and of unusual length compared to the basal margin. The 

 surface of the valve is convex near the umbo ; and beneath 

 there is a large deep hollow for the adductor muscle. 



Terj/a (fig. 1, b) large, flat, triangular, as long as the 

 scuta or the carina, all three valves being nearly equal in 

 length; occludent margin straight, or slightly arched, 

 basal angle broad, not very sharp. 



Carina short (fig. 1, c, drawn rather too long), deeply 

 concave, rectangularly bent, with the lower part not quite 

 as long as the upper, and a little wider : the basal margin 

 is truncated, rounded, and slightly sinuous. The umbo 

 is situated at the angle, and therefore nearly central. 

 The umbo of the terga, I may add, is in the same place, 

 as in Lepas. 



The peduncle is very short and narrow, and is, I believe, 

 without spines ; it is enveloped by the bark of the Anti- 

 pathes. The capitulum in the largest specimens was 

 '2 of an inch in length. 



Filamentary Appendages, apparently none. 



Mouth, with the orifice rather inclined abdominally. 



Labrum, with the upper part extremely protuberant, 

 forming a projecting horn ; no teeth on the crest. Palpi 

 rather small, with only a few bristles at the end. 



Mandibles, with four teeth and the inferior angle 



