52 ^Ir. II. J. Carter on the close Relationship of 



shell like a Biiccinum, and of which I have made a longi- 

 tudinal section througli the columella, leaving what was the 

 mouth of the shell, now marginally covered by the fossil, 

 entire. 



irydmctininph'ocena, Allman (Geol. Mag. No. 98, August 

 1872, p. 337). (PI. VIII. figs. 7-10.) 



Skeleton laminated, thick, incrusting. Composition cal- 

 careous. Colour white. Surface rough, uniformly granu- 

 lated with small conical spines (fig. 9, a, e), interrupted by 

 larger conical ones (fig. 8, a), generally separate, but in the 

 depending parts aggregated into tubercular eminences, over all 

 of tvhich the same granulated surface extends. Granules or 

 small spines obtusely conical and themselves minutely granu- 

 lated, about 1 -200th inch high. Large spines (fig. 8, a) also 

 obtusely conical, numerous, thickly scattered over the surface 

 at unequal distances, about l-30th inch high, and the same in 

 diameter at the base. ]\Iinute circular apertures, varying in 

 size, but averaging l-360th inch in diameter, thickly and 

 generally scattered over the surface between the granules 

 (fig. 8, c) ; granulated surface traversed by deep grooves 

 branching reticulately among the large spines (fig. 8, bb)j 

 the broadest about l-225th inch in diameter. Presenting in 

 the vertical section a confused, laminated, and chambered 

 structure traversed vertically by narrow tubes (fig. 7, bh). 

 Laminaj not distinctly continuous ; chambers compressed, irre- 

 gular in size and position, arched, and often presenting on 

 their floor free conical granules, or small spines, such as are 

 seen on the surface (fig. 9, ddd). Vertical tubes of various 

 lengths (fig. 9, c), about the same diameter as the apertures 

 on the surface, with which in the surface lamina they may be 

 observed to be continuous (fig. 9, i), irregularly constricted in 

 their course, so as often to present a submoniliform appearance 

 (fig. 10) ; constrictions, Avhen viewed in the entire tube, pre- 

 senting a diaphragmatic appearance with central circular hole 

 (fig. 10, a) ; tubes terminating inwardly in apertures of the roof 

 of the chambers (fig. 9, ddd), and outwardly on the floor of 

 the same respectively, as on the surface (fig. 9, c). Small 

 spine or granule solid ; large spine closed at the summit, 

 hollow in the interior, cavity presenting a stellate form in 

 the horizontal section. Size, horizontally, that of the Buc- 

 cinum (fig. 7, a a) or shell over which it has grown, viz. in 

 this instance about 2 inches long by 1 inch broad ; thickest 

 part of incrustation (fig. 7, b) 5-12ths inch. 



Ilab. Marine, incrusting. 



Loc. CoraUine Crag, Suffolk. 



