THE FOSSIL CRICOID GRJSrUS DOLATOCRINUS AND ITS ALLIRS. 7 



brachials. The species represents a retrogression from the older form 

 in the less extent of incorporation of brachials in the calyx, or a 

 progression in the direction of greater freedom of the arms, which- 

 ever way one pleases to consider the case. The chief resulting dif- 

 ference to be noted is in the number and depth of incorporation 

 of the fixed pinnules. Here the arm becomes free at about the third 

 or fourth IIBr. IlBr, has an incorporated pinnule on the outer side 

 of the dichotom, the base of which may also connect by suture with 

 IIBi'g and 4. IIBrg has a free pinnule at the inside of the dichotom, 

 and IIBr^ bears two free pinnules, one from each side. Beyond this 

 in the free arm the pinnules increase to three and four to the brachial. 

 In a specimen with arms the pinnulation can be traced on the out- 

 side of the dichotom to the twenty-second free brachial, and on the 

 inside to the seventeenth. All have at least one pinnule at each side, 

 and about 12 brachials have two pinnules at one or both sides. On 

 bipinnulate brachials the outer pinnule is usually at a different level 

 from the inner. The pinnules are extremely slender, and in the one 

 specimen in which they are partially preserved divide into still 

 smaller branches. The openings for the fixed pinnules are small, 

 round, and project slightly from the edge. The course of the tegmen 

 ambulacra leading to them may be traced by the elongate slits, from 

 which the minute covering pieces have fallen away. (Compare 

 figs. 4 and 10 on pi. 1.) 



Interbrachials in the second range usually two (or only one) in 

 number, with an additional plate between the two at the anal side, 

 usually followed by a single plate in the third range. The anal side 

 is well distinguished in the tegmen by a row of large plates (the 

 largest in the tegmen) having a well-defined median ridge extending 

 from just above the brachial zone to the base of the anal tube; the 

 swollen area widch marks the position of the gut does not coincide 

 with this ridge, but lies asymmetrically to the left of it. The tegmen 

 is highly elevated, strongly bulging at the left posterior; the anal 

 series and some of the axillary ambulacrals sharply pustulose. In- 

 terbrachial plates of dorsal cup may have obscure ornamentation, 

 usually obliterated. 



Horizon and locality .—Hhimlton formation: Clark County, In- 

 diana; Louisville, Kentucky; and Ontario County, New York. 



COMANTHOCRINUS PRISCUS. new species. 



Plate 1, figs. 7-10. 



A species double the size of the type — an average of 8 specimens 

 being about 40 mm. width of calyx at the arm bases. As the tegmen 

 has not been found, the comparative height can not be given. Dorsal 

 cup broad, shallow, and strongly concave. The disparity in size 

 evidenced by the wider spread of calyx in this species is correlated 



