BEEKMANTOWN AND CHAZY FORMATIONS OF CHAM PLAIN BASIN 495 



cording to their general habit and the form and position of their 

 siphuncles, more probably to this than to any other division. 



We have placed all five with the genus Ooceras Hyatt, though only 

 two of them, O . s e e 1 v i and O . 1 a t i v e n t r u m , are good 

 representatives of that genus, as last defined in Zittel-Eastman's 

 textbook. Of the others, O. ( ?) perkinsi shows distinctly the 

 radiating lamellae of the siphuncle [see text fig. 55], characteristic 

 of the xActinosiphonata and is most probably a primitive representa- 

 tive of the Ooceratidae, while the remaining two (O ? kirbyi 

 and O. ? r a e i ) though unknown in their internal siphuncular 

 structures can hardly belong to any other group on account of the 

 ventral marginal position of their nummuloidal siphuncles. Besides 



. ? k i r b y i possesses in its strongly compressed conch and closely 

 set septa additional characters which are developed in the genus 

 Ooceras and make this reference appear fairly correct. Also the 

 faint annulations of O ? r a e i are repeated in several Bohemian 

 species cited by Hyatt as typical members of the genus. Since of 

 the last named species only one or two fragments are known and 

 these come from the excessively hard Beekmantown dolomite of the 

 " Kirby ledge " at Beekmantown, little hope for the collection of 

 additional material can at present be entertained. 



The most striking feature of many (or the typical ?) Ooceratidae 

 lies in their septal necks which are hooklike in section and confined 

 to the dorsal (or inner side) of the conch. This character is well 

 shown in two of the specimens here described [see text fig. 52 and 



P i. 38.] 



Genus ooceras Hyatt 



Ooceras kirbyi Whitfield (sp.) 



Cyrtoceras kirbyi Whitfield. Am. Mus. Nat. Hist. Bui. 1889. 

 2:57, pi. 10, fig. 4-7 



Description. Medium sized, slender cyrtoceracone. The type 

 of the species, a fragment, incomplete at both ends, measures 70 mm 

 and indicates an individual of at least twice that length ; its largest 

 diameter is 34 mm. The conch is strongly compressed ; its section a 

 narrow ellipse with subacute dorsal and ventral sides ; the ratio of 

 the diameters of the section is about 4:7. The rate of growtli is 



1 mm in 65 mm. The curvature is moderate, an inner arc with a 

 cord 32 mm long has a hight of 3 mm. 



The length of the living chamber and the character of the aperture 

 are unknown. The cameras are strongly curved and very shallow, 

 there being counted 6 of them in the space of 10 mm. The sutures 



