No. 89.] 121 



ORTIIIS EMACERATA ( n. s.). 



Shell semiellipti'cal, length and width about as five to seven; hinge-line nearly 

 equalling the width of the shell. Dorsal valve flat, with a slight depression down 

 the centre; area extremely narrow. Ventral valve depressed convex, slightly 

 elevated at the beak, which is inclined over the area, but scarcely incurved; an 

 undefined elevation extending fi-om the umbo towards the front, and sometimes 

 quite to the margin of the shell : area narrow, almost linear. 

 SuREACE finely striated : striae bifurcating, curving upwards, and running out on 

 the hinge-line. Interior of the dorsal valve with two small teeth and a small 

 cardinal process : valves thin. 



This species has the form and general characters of Orthis testudinaria; but the 

 shell is much thinner than that species ordinarily is in the same formation, and the 

 strise are finer, there being at least twenty more on the margin in shells of equal 

 size. The depression in the centre of the dorsal valve, and elevation in the centre of 

 the ventral valve, are far less conspicuous or scarcely marked in some specimens, 

 while the hinge-line is always proportionally longer than in O, testicdinaria. 



Geological formation and locality. In the shales of the Hudson-river group near 

 Cincinnati, Ohio. Received from Mr. Cablet, and also collected in Iowa and 

 Wisconsin. 



ORTHIS ELLA ( n. s.). 

 Shell small, ovate : valves nearly equally convex; hinge-line extremely short, 

 being scarcely more and sometimes less than one-third the width of the shell, 

 and scarcely affecting the contour of the cardinal margin, which slopes from the 

 beak of the ventral to the lateral margins a little above the middle of the valve. 

 Dorsal valve gibbous, subcircular; the beak extending a little above the hinge- 

 line, and the area extremely short. Ventral valve broadly ovate, sloping from 

 the beak : beak produced beyond the line of the opposite valve, and pointed, 

 not incurved; area twice as long as high; foramen narrow and extending to the 

 apex of the beak, and sometimes truncating the extremity. 

 Surface marked by from fifteen to twenty simple, abruptly rounded or subangu- 

 lar plications. 



This small Orthis is so peculiar, as not to be readily mistaken for any other 

 known in our strata. The short hinge-line and area, and the produced beak of the 

 ventral valve, are characteristic features. In some specimens the area is obscure OT 

 undefined, and the shell has much the aspect of Trematospira. It is a rare species, 

 and I have not seen more than twenty individuals, all of which preserve the cha- 

 racters given above, the variation being mainly in the number of strife : those with 

 fewer strise are frequently more gibbous than the others. Length about one-third 

 of an inch; the width a little more. 



Geological formation and locality. In the calcareous shales of the Hudson-river 

 group near Cincinnati, Ohio. From the collections of Mr. S. T. Cakley and Mr. 

 U.P.James. 



OBSERVATIONS UPON A NEW GENUS OF CKINOIDEA : 



CHEIROCRIWUIi. 



I HAVE had in my collections, for the past ten years or longer, some separated 

 plates of aCrinoid so peculiar in character as to convince me that it must be a form 

 very distinct from any thing heretofore described; but I was still unable to arrange 



