250 CATALOGUE OF THE BLASTOIDEA. 



Granatocrinus Derbiensis, G. B. Soiverby, sp. 



(PL VI. fig. 23 ; PI. IX. figs. 1-7 ; PL XI. figs. 11-13 ; PL XVII. fig. 4.) 



Pentremites Derbiensis, G. B. Sby., Zool. Journ. 1825, vol. ii. no. 7, p. 317, t. 11. f. 3 



(4 figs!). 

 Pentremites Derbiensis, Phillips, Geol. York. 183G, pt. 2, p. 207, t. 3. f. 10. 

 Orbit remites Derbiensis, T. & T. Austin, Ann. & Mag. Nat. Hist. 1812, vol. x. p. 111. 

 Pentremites Derbiensis, McCoy, Synop. Cai'b. Lime. Foss. Ireland, 1844, p. 174. 

 Pentremites Derbiensis, McCoy, Brit. Pal. Foss. 1851, fasc. 1, p. 124. 



Pentatrematites Derbiensis, Rocmcr, Archiv f. Naturgesch. 1851, Jalirg. xvii. Bil. i. p. 3G1. 

 Pentremites Derbiensis, Dujarclin & Hupe, Hist. Nat. Zooph. Echinod. 1862, p. 95. 

 Granatocrinus Derbiensis, E. &. C, Ann. & Mag. Nat. Hist. 1882, vol. ix. p. 239. 



Sp. Char. Calyx subglobosc, at times approaching spheroidal ; summit flattened ; 

 base small, concave, and very much contracted ; section roundly pentagonal, with the 

 sides at times a little flattened ; periphery either at or a little above the equator. 

 Basal plates small and confined within the basal cavity. Radial plates small, short, 

 wholly visible in an inferior view, pentagonal, expanding rapidly upwards, lateral 

 margins widely divergent ; limbs short, more or less horizontally truncated above ; 

 sinuses very long and narrow, sometimes almost reaching the basal concavity ; lips 

 very pronounced and projecting ; radio-deltoid sutures variable in position, but 

 always near the base, forming a very wide obtuse angle, and in some cases almost 

 flat, or horizontal ; the union of the basal and radial plates forms a short and wide 

 cup, less than one third the entire height of the calyx. Deltoid plates very large, 

 forming quite two thirds of the entire body, broadly triangular, attenuating slowly 

 upwards, and much curved, with their upper ends almost horizontal, and the apices 

 constricted, the four anterior ones each bearing a node behind the spiracle. Ambu- 

 lacra very narrow, hardly projecting above the general surface of the calyx, and 

 approaching one another somewhat closely at the dorsal pole ; lancet-plate entirely, 

 or almost entirely, covered by the side plates ; ambulacral groove very fine ; side 

 plates small, oblong, very numerous, probably about sixty. One hydrospire on each 

 side of an ambulacrum ; tubes large and wide ; sacs pyriform. Spiracles oval or 

 slightly pyriform, opening inwards and upwards, the anal spiracle larger and more 

 triangular. Mouth small. Column round ; joints long, and cylindrical. Surface of 

 the radial and deltoid plates coarsely granular. 



Remarks. Granatocrinus Derbiensis is noticeable as being the only British species 

 in which the whole of the radial plates arc visible in a basal view (PL IX. figs. 3, 4). 

 The deltoid plates are likewise larger in G. Derbiensis than in any of the others, and 

 in some instances the radio-deltoid sutures are almost horizontal (PL IX. fig. 6). As 

 regards the length of the ambulacra, and their proximity to the basal concavity, 

 G. Derbiensis is intermediate between G. orbicularis (PL IX. fig. 13) or G. ellipticiis 

 (PI. VIII. fig. 18) and G. campanulatus (PL VIII. fig. 13). They are not quite so 



