CORALS OF THE LONDON CLAY. 21 



but irregularly crenulated laterally, especially towards the basis. Height four lines ; 

 diameter one line and two thirds. 



The only specimen of this species which we have seen belongs to the collection of 

 Mr. Frederick Edwards, and is so much filled up with clay at its upper end, that we have 

 not been able to ascertain well the form of the columella and the septa ; we are, 

 however, inclined to think that the columella is slightly compressed, and the septa rather 

 thick. 



Turbinolia Prestwichii differs from all the preceding species by its cylindrical form 

 and broad convex basis ; it differs also from T. sulcata, T. Dixonii, T. pkarelra, 

 T. Nystiana, T. humilis, and T. BowerbanJcii, by not presenting any vertical rows of 

 intercostal dimples ; from T. dispar, T. costata, and T. Fredericiana, by having only three 

 cycla of costae, instead of four, and from T. minor and T. firma, in which the intercostal 

 dimples are equally wanting, by its sharp-edged costae. 



This remarkable species was found at Haverstock Hill, and appears to be very scarce, 

 for Mr. Frederick Edwards, whose collection of London Clay Fossils is extremely rich, has 

 only one specimen of it, and we are not aware of its existing in the cabinet of any other 

 palaeontologist. 



Sub-family of the CYATHININvE (p. xii). 



1. Genus Leptocyathus (p. xiv). 

 Leptocyathus elegans. Tab. Ill, figs. 6, 6 a, 6 b, 6 c. 



Corallum extremely short, nearly discoidal, and presenting, in the adult state, no trace 

 of adherence. Costa distinct from the centre of the under part of the corallum to the 

 calice, strong, projecting externally, cristiform, closely set, rather unequal, separated by 

 rather deep radiate furrows, and rendered echinulate by the presence of a multitude of 

 granulations crowded together (figs. 6a, 6 b). Calice circular, and regularly excavated 

 in the centre. Columella not much developed, and delicately papillose. Septa constituting 

 four complete cycla, closely set, broad, projecting much above and externally ; very thin 

 near the columella, but remarkably thick towards the circumference, and rather unequal 

 (fig. 6 c) ; those of the first two cycla nearly equal, and larger than the others ; the tertiary 

 ones broader than those of the fourth cyclum, but not so high ; all are straight, and none 

 adhere together by their inner edge ; their sides are covered with granulations, which are 

 obtuse towards the circumference of the calice, but become spiniform in the inner part, 

 where the septa themselves are slender. Pali corresponding to all the septa (even to 

 those of the last cyclum, a mode of structure which is very rare), very thin, slightly 

 echinulated, becoming broader as they correspond to younger septa, and appearing to be 

 lobated, as in the genus Paracyathus. Height of the corallum, one line ; diameter, three 

 lines and a half. 



