ICHTHYOCRINIDAE 339 



brachials; anal x often defective or wanting. First iBr larger than the anal, 

 angular above, supporting two rows of large plates in 5 or 6 ranges; illBr pres- 

 ent, and in mature specimens they occur in similar double rows. Column facet 

 very large, sharply and deeply indented, double the usual diameter of the basal 

 circlet excepting the posterior basal, and involving about half the radials ; column 

 composed near the calyx of thin ossicles, diminishing in diameter downward. 



This species is founded upon two specimens in the British Museum, Nos. E7422 and 

 E640, from the Lower Carboniferous at Roscobie, Fifeshire, Scotland, which I have been 

 permitted by the authorities of that Institution to figure and describe. Both are vertically 

 compressed, so that the shallowness of the base is exaggerated. In the principal specimen 

 (PI. XL, figs, 90, b, c) enough of the infolded arms is preserved lying over the top to give a 

 definite impression of their character. The other one (fig. 10) is evidently a mature individual 

 in which the intersecundibrachs are developed into a double series proportionally as large 

 as the interbrachials. A noteworthy feature of the species is the unequal size of the. radials, 

 the two posterior ones being much reduced by encroachment of the very large posterior basal, 

 somewhat as in Parichthyocrinus ; the relatively enormous size of this plate is quite remarkable, 

 when we consider the disproportionate smallness of the posterior area as a whole. 



These two specimens are of somewhat peculiar interest, bearing upon the relation between 

 the presence or absence of infrabasals and the orientation of the axial canal. In figure 10 the 

 infrabasals are small but distinct, and are considerably encroached upon by the axial canal, 

 which is stellate, and its angles are directed interradially ; the same condition exists in another 

 specimen in the British Museum, not figured, having only base and radials preserved. In 

 figure gb, however, and two other specimens since discovered, infrabasals have been entirely 

 resorbed, and the axial canal cutting the edge of the basals is almost radial in position, follow- 

 ing partly the interbasal sutures, and partly the edges of the plates. This is the nearest 

 approach that I know of to a change from a dicyclic to a monocyclic base, accompanied by a 

 corresponding change in orientation of the axial canal. 



I have figured another specimen from Lesmahagow, Scotland, belonging to Mr. R. 

 Dunlap, in the hands of Dr. Bather to whose courtesy I am indebted for the opportunity to 

 examine it ; this gives a better idea of the general appearance of this form than the others 

 (PL XL, figs, no, b). One side of the crown is well preserved as far as the infolding of the 

 arms, but unfortunately the anal interradius above the basal is not visible. The flat surface, 

 and the close interlocking of the rays and their divisions above the interbrachial spaces, are 

 well shown in this specimen. 



Attention must be called to some interesting specimens clearly belonging to this species 

 figured by Ure in his History of Rutherglen, 1793, plate 18, figures 13, 16; — one showing the 

 arms complete from the secundibrachs up, and another a detached base. The figure of the 

 latter does not indicate the posterior basal, but with the scant knowledge of these forms 

 existing at that time it may easily have been ignored in the drawing. The large column over- 

 lapping the radials is entirely characteristic. Ure's account of the first specimen is as follows, 

 page 325 : " Figure 13, Plate XVIII, represents a fragment of Encriims, the supposed head 

 of the entrochi. The specimen from which it was taken was found, along with entrochi, 

 shells, etc., in till incumbent on limestone at Hermayers, and it is the only one of the kind. 

 The pieces of which it is composed are joined to one another by suture." 



After the foregoing description was written Mr. James Wright, Jr., of Kirkcaldy, Scot- 

 land, published figures of several specimens of this form under the name Forbesiocrinus, 

 without description or specific name. Later on he most courteously sent me for examination 

 his entire collection of Flexibilia, found quite recently at Roscobie and Inverteil, Fifeshire, 



