﻿AMERICAN TERTIARY AND CRETACEOUS FOSSILS. 403 



by about ten heavy, longitudinal ribs ; sutures obliterated ; opening small, tubulate 

 and inclined in the direction of the curve. 



Dimensions. — Length about '25 in., greatest diameter *03 in. 



Locality. — Near Mullica Hill, N. J. My collection. Rare. 



OSTREA, Linn. 



O. tecticosta. PI. 68, figs. 47, 48. Elongated, irregularly oval, arcuate; beaks 

 acuminate ; ligament area triangular, oblique; muscular impressions rather large; 

 lower valve generally attached, deep, usually deepest along the median line, but 

 becoming flattened towards the basal margin ; surface marked by numerous promi- 

 nent, imbricating ribs, radiating from the middle line and not from the beaks ; upper 

 valve not so deep as the lower ; surface only marked by the usual lines of growth ; 

 upper half of the internal margins of both valves denticulate, corresponding in 

 the lower valve with the external plications. 



Locality. — Cretaceous. Tennessee and New Jersey. My collection. 



This species was sent to me last Spring, by Prof. Safford, when I referred it pro- 

 visionally to 0. larva, ( 0. falcata, Morton,) thinking it might be one of the many 

 varieties of that species. I am now, however, satisfied that it is distinct. It is wider, 

 the plications on the lower valve are more numerous, and have a different arrange- 

 ment from 0. larva and are imbricating, and the upper valve is not plicated. It has, 

 besides, no alations near the beaks as in Lamarck's species. I have one specimen 

 of a lower valve from New Jersey, kindly given me by my friend, Mr. C. C. Abbott. 



BRYOZOA. 



ACERVICLAUSA, n. g., Gabb and Horn. 



Colony tubular, probably encrusting, consisting of numerous superposed layers, each 

 layer covered with cells, surrounded by a space in which are no cellules ; cellular 

 margin slightly elevated, interspace of cells depressed. 



Relations. — This genus is established from several well preserved specimens of one 

 species, and appears to occupy a. place intermediate between Multiclausa and Semi- 

 multiclausa. The specimens are tubular and coarsely striate within. 



A. vermicularis, G. and H. PI. 69, figs. 42, 44. Colony tubular, nodulate ex- 

 ternally ; cells small, uniform in size, with one side flattened, and with a tendency to 

 an irregular, transverse linear arrangement. In the specimen figured there are eight 

 layers of cells superposed. 



Locality. — Near Mullica Hill, N. J., in the deposit mentioned above. My collec- 

 tion. Presented by Mr. Abbott. Rare. 



