1870.] 289 [Burgess. 



Left clasp : Main body very broad, increasing slightly in breadth 

 from the base half way to the tip, nearly flat and straight, the upper 

 edge produced and curved inward a little near the base, the lower 

 edge a little full near the base. Blade straight, its lower edge con- 

 tinuous with the lower edge of the main body, slender, uniform, 

 slightly compressed, not very long, armed at the apical half with 

 minute, raised points, and terminating in a rounded point; basal 

 process as broad as long, rounded, compressed, its hinder two thirds 

 bent at right angles inwards and a little upwards, and armed along 

 its whole edge and a portion of its upper surface with minute spin- 

 ules. Lobe rounded, deeply and roundly excised on either side, of 

 about the size of the basal process of the blade, but smooth; just in 

 advance of it the upper edge of the main body is slightly prominent. 



Right clasp : Main body similar to that of opposite side. Blade of 

 the same length as that of the left clasp and otherwise similar, but 

 curving very slightly inward and terminating in an unarmed slightly 

 rounded point, a very little angulated at the tip; basal process devel- 

 oped as a dactylate apophysis, directed upward, nearly at right 

 angles to the blade, compressed, but twisted at right angles, so as to 

 appear depressed, a little broader than the blade, shorter by nearly 

 one half, its tip broadly and regularly rounded, and armed with mi- 

 nute spinules. Lobe developed as a bluntly rounded, rather promi- 

 nent plate in the middle of the upper half of the whole piece. 



New England. 

 Nisoniades Brizo Westwood. Fig. 4. 



Upper organ: Main body moderately slender, long and high, 

 strongly arched ; from the middle of the extreme posterior slope of 

 the upper surface, a lateral, triangular, slightly curved plate or ala- 

 tion with rounded apex, arises on either side, projecting outward and 

 a little upward, the anterior edge nearly at right angles with the 

 median line of the main body, or even directed a little forward, and 

 a little elevated. Hooks united into one extremely large beak, swollen 

 beyond the middle, the tip pointed, the sides at base compressed and 

 directed downward as small flaps ; beyond the middle of the lower 

 surface depends a very large, appressed tooth, the anterior edge nearly 

 straight, the posterior curved sinuously forward, as seen from the 

 side, broad and well rounded, the posterior surface having the edge 

 emarginate, and furnished with a slight median ridge. Arms ex- 

 tremely broad at origin, tapering very rapidly in a downward direc- 

 tion, becoming slender before the lowest point is reached, and then 



PBOCEEDINGS B. S. N. H.— VOL. XIII. 19 AUGUST, 1870. 



