400 The CalceocrinidcB. 



The articular joint consists of two deep grooves in the opposite mar- 

 gins, the outer edges of which are widely separated when the crinoid is 

 in its normal position of rest, while the inner two are in close apposi- 

 tion. Over these inner margins pass two bundles of elastic ligaments 

 from one groove to the other. 



They each arise in two parts from both sides of the termination of 

 the two suture-lines of the anterior radial; one part coming from the 

 anterior radial and the other from the adjoining lateral radial. These 

 two parts or heads unite and pass over the inner margins of the two 

 adjoining grooves, and are inserted into the groove of the consolidated 

 basal piece, directly opposite their points of origin. 



Faint traces of the integument uniting the two outer margins of the 

 grooves and covering the elastic ligaments, can be seen. This integu- 

 ment is better shown in some other specimens of P. radiculus, in one 

 of which it is broken up into small pieces which at first glance have the 

 appearance of " numerous little plates," such as are figured by Ulrich 

 in " Cremacrinus " punctatus. 



The vault is covered by four projections from the inner sides of the 

 four plates entering into the formation of the rim of the calyx proper. 

 The top of the vault is smooth and evenly convex, its central portion 

 being depressed to a point opposite one-half the height of the lateral 

 radials, when measured from their lower to their upper angles. The 

 only suture-lines observable are those commencing from the four 

 suture-lines dividing the four plates, which proceed directly from their 

 point of origin to the centre of the vault, where they all meet. 



This arrangement gives three large triangular projections and one 

 narrow wedge-shaped one. The outline of the concave space is round- 

 ing on the anterior side, with two lateral projections or grooves along 

 the suture-lines, and one such groove in the centre posteriorly. 



In the margins of the two lateral radials, can be observed two narrow 

 slits which represent the continuation of the arm-grooves. 



I was at first inclined to consider this vault as a kind of partition, 

 serving to strengthen the calyx and taking the function of the basal 

 plates, which no longer served to maintain its rigidity. 



Prom the lower third of the shale at Lockport, N. Y. 



The revision of the genus Galceocrinus we will preface with 

 a few introductory remarks concerning the original species upon 

 which the genus was founded. 



The original description speaks of the semicircular base as 

 consisting of two pieces ^'anchylosed" (consolidated) together, 

 a triangular one fitting into a somewhat lunate-shaped piece. A 

 more careful examination of two specimens of the same portion 

 of this species, shows a secondary suture-line starting from the 



