28 ACANTHOCHITES. 



ulate, surrounded by a wide smooth band. Girdle tawny, ornamented 

 with gleaming white, glassy tufts. 



Length 35, breadth 20 mill. (Rochebr.} 



Strait of Magellan. 



Acanthochiton stygma ROCHEBR., Miss. Sci. du Cap Horn, vi, 

 Zool., p. 134, t. 9, f. 2a, 2b (1889). Not C. stigma Costa. 



It is evident that but little dependence can be placed on the 

 figures of this species. 



A. BISULCATUS Pilsbry, n. sp. PL 4, figs. 86, 87. 



Oblong, elevated, carinated, the side-slopes flat and straight. 

 Buff, maculated with olive-green and dark green, or greenish with 

 dark green and blackish mottling. 



Anterior valve having the evenly granulated tegmentum extend- 

 ing two-thirds of the distance to the edge of the teeth. Intermediate 

 valves (fig. 87) having a very broadly heart-shaped tegmentum ; 

 the dorsal area triangular, convexly raised, longitudinally striated. 

 Later o-pleural areas distinctly concave or hollowed out on each side of 

 the dorsal area; covered with rather thickly distributed, drop- 

 shaped flat or concave pustules (fig. 86) averaging about one-sixth 

 of a mill. long. Posterior valve having the tegmentum symmetrically 

 oval, the long axis of the oval transverse to that of the animal ; 

 mucro prominent, subcentral. 



Interior bluish. Insertion-plates and teeth normal. Tract behind 

 the sinus spongy. Posterior valve having one slit on each side, but 

 hardly a perceptible sinus behind. 



Girdle rather wide, densely clothed with whitish spinelets, and 

 having 9 tufts on each side. 



Length about 22, breadth about 9 mill.; divergence 100-110. 



Habitat unknown. 



Although the habitat of this species is unknown to me, I antici- 

 pate no difficulty in its recognition. The shallow but distinct sulcus 

 on each side of the dorsal area is a diagnostic feature, but unfortu- 

 nately is not shown in the figure. 



(5) Undetermined, and unrecognizable species of Acanthochites. 



ACANTHOCHITES TRisTis Rochebr. Shell broad, ovate, sooty, 

 carinated, subumbonate. The anterior valve rounded, posterior 

 swollen ; intermediate valves having the central areas transversely 

 roughened ; lateral areas with sparse, wide tubercles. Girdle wide, 



