lOO DAVENPORT ACADEMY OF NATURAI. SCIENCES. 



node, there are two or three smaller nodes which extend more or less 

 from the first or second radical to the succeeding plates. 



Geological position, locality, etc.: The type specimens from which 

 the above description was made were gathered by the writer from rocks 

 of the age of the Hamilton grou]), at Alpena, in Northern Michigan, 

 and are now in his collection. 



DoLATOCRiNus TRIADACTVLUS BarHs, Nov. Sp. 



Plate II. — Fig.S- Dorsal view. 



Fii{. b. Side and part of dorsal view. 



Fig. 7. An individual, showinsf arms, three to the ray. 



Body small, depressed at the dorsal side, sHghtly elevated at the 

 ventral side; width smaller than the height. Calyx broadly basin- 

 shaped, with a truncation around the base, which includes the whole of 

 the first radials, half of the second radials, and the lower part of the 

 first interradials. Dome in form of a low cone, interradial portions 

 along the sides deeply depressed, the radial region extending outward. 

 There is no appreciable distinction between the anal and interradial 

 series. 



Basals three, unetjual in size, firmly anchylosed, forming a funnel- 

 shaped concavity for the reception of the column. The first and sec- 

 ond radials constitute the bottom part of the calyx, and take little or 

 no part in forming the lateral walls. 



The first radials are hexagonal, narrow at the base, the inner margin 

 of which bends slightly into the columnar cavity, its three upper sides 

 somewhat concave. Second radials smaller than the first, quadran- 

 gular, broader than high, upper and lower edges straight or convex. 

 Third radial pentagonal, slightly wider and higher than the second; 

 supporting on its upper sloping sides, at one side two radials of the 

 second order, the first large, the second smaller, at the other side 1x2 

 tertiary radials, with one arm at the one side and two at the other, or 

 three arms to the ray, /. e., fifteen in all. These arms are simple, com- 

 posed of a double series of rather thick, short joints interlocking with 

 each other. 



Interradials two; the first one as large as the first radial, sub-ovoid, 

 resting against the curved sides of two first radials, bordered by the 

 second, and reaching nearly up to the height of the third. Supported 

 on its upper curved side is the second interradial, >vhich is smaller and 

 quadrangular. There are two or three small plates above, between the 

 arm bases. 



