part 3] CEROIDS from new Zealand. 25B 



pentapetalon), passing from the intermdius towards the peripheiy 

 at an angle which gradually increases to a right angle in the more- 

 acentral ridges : all continent on the periphery. 



Syzygial face (seen in one imprint, tig. 11, whether epi- or hypo- 

 zygal uncertain): sides of rounded pentagon faintly excavate ; lumen, 

 and central area larger than in the normal face, the area slightly 

 raised ; petal-floors wide, and flush or slightly depressed ; perradial 

 ridge-groups 2, the adcentral one a mere granule, the acentral one 

 lambdoid with the stem hroadening to form part of the peripheral 

 rim ; peripheral crenellse restricted to one on each side of the lamb- 

 doid stem, but the rim is continuous, though faint, and a couple of 

 slight swellings on it represent the interradial crenellse. 



There is one small imprint (tig. 10) that appears to be of an 

 epizygal, but it is not very clear. It is a rounded star, with, 

 diameter = 1*8 mm. ; IR = 1 mm. ; r = 0*5 mm. ; lumen minute, but 

 distinct, relatively large, apparently pentagonal ; lidges invisible ; 

 petal-floors slightly depressed; rim indistinct. The side-faces of 

 this columnal were vertically concave, and apparently bore a 

 depressed, elliptical cirrus-facet. 



Cirrals appear to be represented by imprints of a few small 

 canaliculate ossicles. 



Brachials. — There are a few scattered imprints of articular 

 faces, which probably represent brachials, of this species. There 

 are w^ide brachials from the proximal region (tig. 12), narrower 

 and more elevated ones from the distal region (tig. 13) ; one wide 

 brachial shows a syzygial face. All have the axial canal well 

 ' developed, and in this respect resemble the brachial from the 

 Raiblian Car di fa-Oolite of Rammelsbach, tigured in ' Triassic 

 Echinoderms of Bakony ' (1909, pi. v, tig. 122) rather than the 

 brachial from the Cassian Beds of Cserhat (oj). cit. pi. v, tig. 127). 



Relations of the species. — The joint-faces of three EuroiDean 

 Triassic species (/. j^^^opinquiis^ I. hercunice, I. havaricus) are 

 distinguished from I. trechmanni by the presence of a radial 

 triangle. The absence of a rim and the consequent crenelation of 

 the suture-line distinguish /. fyrolensis, I. scipio, and I. sceptrum. 

 I. amoenus is further characterized by the marked ornament of its- 

 side-faces, and I. candelahrum by the long curved ridges of its 

 joint-face. In I. duhius (Goldfuss) the crenellse are confluent 

 with the peripher}^, but that species, to judge from the original 

 figures, has wider petal-floors than I. trechmanni, with a greater 

 distinction between the radial ridge-groups and the peripheral 

 ridges. I. duhius needs careful redescription on the basis of the 

 original material ; meanwhile, it is with it and similar forms that 

 I. treclimanni should be associated. 



Turning to the Triassic species of North America, the characters 

 of which have latel}^ been sketched by Prof. VV. B. Clark (1915), 

 we find three species, which may be discussed briefly. 



Isocrinus smithi, from the Lower Trias, is represented b}^ 

 weathered columnals. The section in the specimen as tigured is a 



Q. J. G. S. No. 291. X 



