124 DICHELASPIS GRAYII. 



Terga. — These valves are of the most singular shape, 

 resembling a battle-axe, with a flat and rather broad 

 handle ; the upper part consists of an axe, with a broad 

 cutting crenated edge, behind which is a short blunt 

 spike. The spike and cutting edge together answer to 

 the double occludent margin of the tergum in Lepas. 

 The whole valve is flat, thin, and lies in the same plane ; 

 the carinal margin is nearly straight ; the scutal margin 

 bulges out a little, and at a short distance above the blunt 

 basal point is suddenly narrowed in, making the lower- 

 most portion very narrow ; the widest part of the handle 

 of the battle-axe, is narrower than the occludent segment 

 of the scuta. The two spikes behind the cutting and 

 crenated edges of the two terga, are blunt and almost 

 touch each other ; above their point of juncture, the mem- 

 brane of the orifice forms a slight central protuberance. 



Carina, very narrow throughout, concave within, much 

 bowed ; upper point broken and lost, but it must have 

 run up between the terga for more than half their 

 length ; basal portion inflected at nearly " right angles, 

 and running in between, and close below, the linear 

 basal segments of the scuta, so as almost entirely to 

 cut off internally the peduncle and capitulum. This 

 lower inflected and imbedded portion, or disc, gradually 

 widens towards its further end, which is, at least, four times 

 as wide as the upper part of the carina, and is deeply 

 excised, but to what exact extent I cannot state, as the spe- 

 cimen was much broken. On each side of this elongated 

 triangular disc, there is a slight shoulder corresponding 

 to the ends of the basal segments of the scuta; and on 

 the upper surface of each shoulder, there is a small tooth 

 or projection. The middle part of the disc is barely 

 calcified, and is transparent. 



Peduncle, rather longer than, and not above half as 

 wide as, the capitulum; the latter being nearly T Vths 

 of an inch in length • the membrane of the peduncle is 

 thin, naked and structureless. 



Mouth. — Labrum highly protuberant in the upper part, 



