36 THE CRAG POLYZOA. 



elliptico^ subinde trifoliato ; peristomate piano. Cellulis pluribus, aviculario medio infra 

 aream depressara posito, armatis. Ovicellulis parvis, prominentibus, rostro sulcato miinitis. 

 Polyzoarium spreading irregular ; cells pyriform ; upper two thirds of front occupied 

 by a broad oval space, bounded by a ridge, within which the surface is depressed ; orifice 

 suborbicular, elliptical, sometimes trifoliate ; margin level ; a crescentic pore on each side 

 of the depressed area ; surface smooth ; an avicularium on many cells on the median line 

 in front below the area ; ovicell small, prominent, with a sulcate rostrum in front. 



EscHARiNA (Cellepora oceani), D'Orbigmj, Pal. Franc. (Terr. Cret.), pi. dcv, fig. 14. 



Habitat. — C. Crag, inside of a small Astarte Omalii, and of a small Pecten. 



The trifoliate foiin of the orifice, or, more properly speaking, of the aperture occa- 

 sionally noticed in this species, appears to be due to an arrest in the calcification of the 

 lamina filling up the oval area on the front of the cell ; the lateral leaflets of the opening then 

 representing the lunate pores visible in the cells where the calcification has proceeded to 

 its full extent. With this form of the aperture, and the presence of the median avicularium 

 at the lower half of the cell, M. oceani exhibits characters in common with M. trifolium, 

 but attentive consideration has satisfied me that the two are distinct. 



Of the identity of M. oceani with M. D'Orbigny's species, little doubt can be 

 entertained on comparison with his figure, notwithstanding the great diflference which 

 would seem to exist in the respective ages of the rocks in which they occur. 



14. M. HOLOSTOMA, S. W. PI. Ill, fig. 11. 



Polyzoario irregulari ; areis cellularum ovalibus, pyriformibus, subhexagonis, vel supra 

 arcuatis et latioribus, infra angustioribus, apice truncatis ; septis valde elevatis, granulosis, 

 longitudinaliter sulcatis; lamina superficie granulosa utrinque medium versus perforata ; 

 orificio suborbiculari, peristomate elevato; aviculariis magnis, ellipticis, numerosis inter 

 cellulas dispersis. 



Polyzoarium irregular; front of cell oval, pyriform, subhexagonal, or arched and 

 expanded above, contracted below, and truncate at bottom ; margin much raised, granular; 

 a distinct line of separation between the margins of contiguous cells ; surface of lamina 

 granular ; orifice suborbicular, peristome raised ; an elliptical pore on each side about the 

 middle ; numerous large elliptical avicularia between the cells. 



Flustra HOLOSTOMA, S. W., Ann. N. II., xlii, p. 20. 

 Habitat. — C. Crag, S. IF., on inside of a small Pcctunculus glycimeris. 



