MOUNTAIN LIMESTONE FOSSILS. 201 



easily from any other Diphyphyllum I know, and gives the whole 

 much the appearance of Siphonodendron aggregatum (M'Coy), but 

 the lamellae do not extend nearly to the centre ; there is no axis, 

 and the dichotomous fission of the star and tubes may be di- 

 stinctly observed. 



Not uncommon in the impure limestone of Lowick, Northum- 

 berland. 



[Col. University of Cambridge.) 



Clisiophyllum turbinatum (M'Coy). 



Sp. Char. Corallum simple, turbinate, very rapidly enlarging, 

 attaining the adult diameter of about 1| inch at 2 inches from 

 the point of attachment ; surface of the strong external wall or 

 epitheca marked by coarse, numerous, imbricating transverse 

 striae, and a few larger inequalities of growth (no distinct lon- 

 gitudinal striae except when abraded) : horizontal section, cen- 

 tral area or axis nearly equalling one-half the diameter of the 

 coral, composed of a close crumpling of fine vesicular plates, 

 crossed by a few radiating irregular extensions of every fourth 

 or fifth of the radiating lamellae, one of which, stronger than 

 the rest, is usually seen to cross the middle (forming a thick 

 mesial line in the vertical section, and a prominent crest in the 

 cup) ; lamelliferous axis rather less than one-third of the whole 

 diameter, radiated by about fifty-four strong, equal lamellae 

 (at a diameter of 1 inch), connected by numerous delicate 

 transverse vesicular plates ; four lamellae in the space of 2 lines 

 near the margin ; outer or perithecal area less than one-fourth 

 the width of the lamelliferous zone, from which it is separated 

 by a thin definite boundary ; it is composed of about two ob- 

 scure rows of small, compressed cells, more or less crossed by 

 costal extensions of the lamellae : vertical section shows a strong, 

 solid line down the middle of the axis or middle area, a thinner 

 solid line defining the axis on each side, and a similar one be- 

 tween the middle and external areas ; external area very nar- 

 row, of about two rows of minute cells ; middle of about three 

 rows of large rhomboidal cells formed of thin, moderately 

 curved vesicular plates converging upwards and inwards at a 

 low angle ; inner area composed on each side of about three 

 rows of cells, converging upwards to the mesial line, much 

 smaller and more compressed than those of the middle area : 

 terminal cup of moderate depth, lined by the thick, equal, ra- 

 diating lamellae, the axis forming a moderately prominent boss 

 in the bottom, crossed by a small prominent crestiform plate. 



This is easily distinguished from the other known species 

 by its short, rapidly expanding turbinate form; it resembles 



