384 SMITHSONIAN INSTITUTION 



Column large, flush with base, expanding toward calyx; columnals very thin 

 for the short cone at top, becoming longer downward, with but little, if any, 

 alternation. 



The description is made chiefly from the figures and descriptions given by Rev. G. F. 

 Whidborne in his Monograph of the Devonian Fossils of the South of England. He had 

 before him all that was left of Phillips's type specimens, viz., the original of his figure 412 

 (Palaeozoic Fossils of Cornwall, pi. 15) now in the Museum of Practical Geology, London, 

 of which in its present condition he gives a good figure. I have copied this (PL LI, fig. 2), 

 along with Phillips's original figure of the same specimen (fig. 1). Owing to the lack of 

 technical accuracy in the older figure these appear but little alike, yet there is no doubt of 

 the identity 'of the specimen. It has suffered some injury, the preservation being poor and 

 fragile, as in many of the crinoids of the English Devonian, where they occur partly in the 

 form of casts or natural moulds, often in rather friable material. The primibrachs below 

 the axillary are gone, but Phillips's figure, in which there was no attempt at restoration, 

 clearly shows that there were originally three plates below it. 



I also copy another of Phillips's figures, 41 b (fig. 3), from a specimen now lost, showing 

 three primibrachs, and giving a general idea of the stem. Supplementing these is Whid- 

 borne's figure of another specimen (figs. 40, b) which gives the characters of the stem and 

 base. These specimens thoroughly confirm the description given by Phillips of the charac- 

 ters assigned to this species, the study of which led him to recognize in it a new generic type. 

 His descriptions and accompanying remarks are as follows (Pal. Foss. Cornwall, p. 29) : 



The pentagonal supra-columnar joint is surmounted by five plates (pelvis of Miller), alternately 

 with which, and above them, are five rows of broad costal and scapular plates, four in each, the last being 

 cuneiform. From this point, the hands and fingers go on dividing, and the number of joints in each 

 successive branch augments. The arms, hands, and fingers are externally round ; the finger ends are 

 cirrhose. 



On comparing this form with Poteriocrinus (?) Egertoni, Poterioc. nobilis, Cyath. tuberculatus, &c, 

 it appears that they are congeneric; and that, unlike other Cyathocrinitcs and Poteriocriuitcs, they might 

 be characterized by having the scapular, costal, and cuneiform arm base in one row and of one breadth. 

 Perhaps Actinoc. (?) expansus, of Sil. Researches, may be allied to them. If, provisionally, we designate 

 this group by the title of Isocrinites, and consider the specific characters as depending on the number of 

 plates in the costal, brachial, and digital series, we shall find 

 Isocrinus Egertoni, to have seven costals ; 



tuberculatus, three costals and three brachials ; 



macro dactylus, four costals, five brachials, and six, ten, fifteen digitals ; 



nobilis, four costals, four or five brachials, and four, &c, &c, digitals. 



It must, however, be remarked that above the costal rows the numbers of brachial and digital joints 

 vary in the same specimen, owing to an unequal development which is almost always remarked in these 

 fossils. In hoc. macro dactylus the first digitals are six or seven. Another difference arises from age, as 

 remarked in Sil. Researches, in relation to Cyath. tuberculatus; and in Geol. of Yorkshire, in regard to 

 Poteriocrinus. 



This description also points out the chief difference between this and the only other of 

 his species now remaining in the genus, T. nobilis, viz., the longer arm divisions. 



There is no mention of the anal structures, either in this or in Whidborne's redescription, 

 as none of the specimens show them. 



The geological position of the species is late in the Devonian — the Pilton beds being now 

 classed as Upper Devonian, or at least not later than the equivalent of the Hamilton of this 

 country. 



Types. Phillips's original of his figure 41 e, and that of figures 4a, b herein, are in the 

 Museum of Practical Geology, London. The other specimen figured by Phillips cannot be 

 found. 



Horizon and locality. Upper Devonian, Pilton beds ; Pilton, and North Devonshire, 

 England. 



