part 3] CRiNOiDs feom js^ew zealajS^d. 255 



[I am indebted to the Director of the United States G-eological 

 Survey for several sets of squeezes taken from the best specimens 

 found in Alaska (Gr. C. Martin, 1916). It is inferred from these 

 squeezes that the original specimens are in their natural relief. 

 Plaster casts have therefore been taken from the squeezes in the 

 Geological Department of the British Museum, and form the basis 

 of the following descriptions : — 



IsocRiNUS cuPEEUS, sp. nov. (Fig. 14, p. 248.) 



Tmnsverse section a rounded star, with the sides of the inter- 

 radial angles slightly convex. Normal joint-face with lumen 

 minute (under 0*25 mm.) and central area raised in a rim round it ; 

 petals broadly lanceolate, floors flush with the ridges or but slightly 

 lower ; radial ridge-groups about 4, their crenellse inosculating, 

 and apparently fragile, merging into peripheral crenellse, which 

 are 8 or 9, non-contluent. Suture crenelate all round. 



Approximate measurements : — IK = 2*5 mm. ; r = 1-5 mm. ; 

 reentrant angle = 0*5 mm. ; making diameter =4'5 mm. 



Locality. — Jumbo Creek, near Bonanza Mine, Copper River 

 region, Alaska. U.S. Geol. Surv. Loc. 4809. 



Horizon. — Upper Trias, Chitistone Limestone, supposed to be 

 Middle or Upper Carnic, therefore comparable with Raiblian (see 

 G. C. Martin, 1916, p. 692). 



Material. — Squeezes in various substances from specimens in 

 the collection of the U.S. Geological Survey, and plaster casts 

 taken therefrom in the British Museum, Geological Department. 

 Registered E 21915-21918, E 22178-22180. 



Holotype. — Plaster cast E 22178 and its original at 

 Washington. 



Relations. — The most striking feature in the fossils (as inter- 

 preted from the squeezes) is the hollow that in nearly ever}" radius 

 of every specimen occupies the position of the radial ridge-groups. 

 At first, this suggests a radial triangle ; but closer inspection shows 

 that crenella^ exist all round the periphery, and in rare cases, as m 

 the right upper radius of fig. 14, the radial ridge-groups still 

 remain. It appears as though these structures were of looser 

 texture than usual, and so were easily worn or broken away, leaving 

 as a rule obscure traces or even a mere hollow, as in the left upper 

 radius of fig. 14. This last appearance seems (on the evidence of 

 the squeezes) to be the most chai-acteristic, and though it is not 

 in the strict zoological sense a diagnostic character, it may be 

 regarded as distinguishing what Prof. H. S. Williams (October 

 1917) has called a 'metamorphic species.' ^ The visible character 

 of such a s])ecies is directly due to certain physical, mechanical, or 

 chemical conditions of fossilization or metamorphism ; but for it to 

 have any systematic value, it must be indirectly due to some 

 feature in the gross or minute anatomy. That feature may have 

 been invisible until made visible by the exti-aneous forces, which 

 act as do the differentiating reagents of the laboratory. 



^ • Xucixlites from the Silurian, &c.' Proc. U.S. Nat. Mus. vol. liv, pp. 27-58. 



