LONSDALE ON EOCENE CORALS FROM N. AMERICA. 527* 







but as the figures given by these authorities differ greatly from 

 that more recently published by M. Michelin (Icon. Zoophy. pi- 46. 

 f. 21.), unaccompanied, however, it is to be regretted, by the des- 

 criptive details which would have removed all difficulties, the com- 

 piler of these notices refrains from assigning any specific appella- 

 tion to the American coral. The chief distinction between De 

 France or G-oldfuss's figures and the specimens under considera- 

 tion, consisted in the narrowness of the central depression, a cha- 

 racter probably due to changes incident upon age. In one not 

 very satisfactory case, the cavity was apparently filled up, a minute 

 puncture without any raised margin indicating the position of the 

 mouth. 



Locality. — Rock's Bridge. 



18. HlPPOTHOA TUBERCULUM. (sp. n.) 



Cells pear-shaped, variously arranged ; connecting tubuli generally short or 

 wanting, rarely long; membranous aperture large, oval; solid surface or walls 

 smooth, convex ; a minute tubercle near proximal extremity of aperture. 



In the form of the cells, and the 

 characters of the membranous 

 opening this fossil resembled 

 greatly the recent Hippothoa 

 catenularia of Dr. Fleming (Brit. 

 Anim. p. 534.) ; but in numerous 

 specimens of that coral obtained 

 on the coasts of Devon and 

 Cornwall, a minute tubercle near 

 the aperture was in no instance 

 detected. In two cases this pro- 

 jection was replaced, probably on 

 account of abrasion, by an equally 

 small cavity. 



With respect to the large open- 

 ing covered in the recent state, as 

 mentioned by Dr. Johnstone, with 

 a membrane (Brit. Zoophytes, p. 

 265.), cases were observed in the 

 American fossil of what appeared 

 to be a partial and even a total 

 obliteration (see fig. a) ; and in a 

 specimen of Hip. catenularia, the 

 membrane in a few instances had 

 become white and opaque. 



This figure of Hippothoa tuber- 

 culum exhibits (greatly enlarged) 

 the general mode of growth, and 

 the tuhevcle or cavity at the proximal 

 end of the oval aperture. At a are 

 cells with the surface wholly covered. 



been so thickened as to have 



Locality. 



Rock's Bridge. 



N N 2 



