DESCRIPTIONS OF THE BPECTES. 256 



(PI. VI. fit^'. 21), niiuo so than in any other species of the genus, except perhaps 

 G.\ granulatus, Roemer 1 (PI. VI. fig. 22); but it is rarely preserved at all well. 



We are acquainted with two well-marked varieties of G. ellipticus, both of which 

 were originally illustrated by Mr. G. B. Sowerby, though only one was figured by 

 Prof. Phillips. In one of these (PI. VIII. fig. 16) the radio-deltoid sutures are 

 straight and direct, forming a large open V 2 . In the second variety, however, these 



sutures are gracefully curved upwards (L'l. VIII. fig. 19) so as to form a V resembling 

 a "broad arrow " :i . In the variety with the straight sutures there is a corresponding 

 increase in the width of the upper portion of the calyx, the summit being by no 

 means so contracted as in the other form. A small and more coarsely granular 

 example of this type is shown on PI. X. fig. 16. 



Many of the fragmentary and more or less weathered specimens of G. (Ilijiticvs in 

 the Rofe collection have been of the greatest importance to us in elucidating obscure 

 points of structure (PI. VIII. fig. 20; PI. X. figs. 12-15). These have been already 

 explained on pp. 48-50, 92, &c. 



Localities and Horizon. Bolland District, Lancashire ; Clitheroe, Lancashire 

 (Presented by the late J. Rofe, Esq., F.G.S.) ; Preston, Lancashire: Carboniferous 

 Limestone. [Prof. McCoy quotes this form as an Irish species, but does not record 

 the locality.] 



Genus HETEROBLASTUS \ gen. nov. 



Gen. Char. Calyx generally resembling that of Granatocrinus in the form and 

 proportion of its component parts. The proximal ends of the deltoids are produced 

 upwards as short stout processes, with their bases notched by the spiracles which 

 lead into canals lodged in grooves on the inner faces of the deltoids. Radial sinuses 

 wide, their edges sloping gently downwards to the slightly petaloid ambulacra. 



Remarks. We have established this genus for the reception of a single species of 

 very remarkable character, which differs in the structure of its spiracles from any of 

 the preceding genera. 



The material at our disposal is not very well preserved ; but it is sufficient to show 

 the relations of the deltoid plates and spiracles. The proximal ends of the deltoids 

 are produced upwards into short and blunt spine-like processes, some of which 

 occasionally seem to be in two parts (PI. VI. fig. 3), though we do not think that 

 this is really the case. A minute lateral opening is visible at the base of each 

 process, between it and the ambulacrum ; and an internal view of an isolated deltoid 

 plate (PI. VI. fig. 4) shows that these openings lead into gutter-like channels, exca- 

 vated in the substance of the plate for the reception of the proximal ends of the two 

 hydrospire-canals. In the posterior intcrradius, however, there seems to be a single 

 1 Archiv f. Naturgesch. 1851, Jahrg. svii. Bd. i. p. 363, t. iii. f. 13. 

 - werby's two upper figs. he. cit., and Phillips's middle fig. he. cit. 

 3 Sowerby 's middle fig. loe. eit. * trepos, unusual. 



