4/2 



NEW YORK STATE MUSEUM 



Siphuncle tubular, large, one fifth the hight of the volution, 

 propioventran in the last whorl. Shell smooth, growth lines strong, 

 receding on sides ; living chamber with low ribs. 



Position and locality. In A 3 of the Fort Cassin beds of the Yal- 

 cour section. 



Observations. This species is most closely related to T . e x - 

 t e n s u m Hyatt, a species which occurs in the Beekmantown beds 

 of Port au Choix, Newfoundland. Both forms have in common the 

 rate of growth and the sections of the volutions, the position and 

 size of the siphuncle, but T . c 1 a r k e i can be readily distinguished 

 from the Newfoundland type by the more concave septa and their 

 iess close arrangement (one half as close as in T . extens u m ) . 

 Also the paragerontic volution is more rapidly evolving and straight- 

 ening in the other form. Still the two species are so similar by the 

 identity of their principal characters that a close relationship seems 

 evident. From T . s e e 1 y i , to which it also bears some similarity, 

 it differs in the uncoiling of the last volution, greater rate of growth 

 and wider and more ventrally situated siphuncle. Also the cameras 

 are somewhat deeper in this species (ratio of the number of septa 

 within a certain space in the two species as 4:3). 



Tarphyceras multicameratum sp. nov. 



Plate 19, fig. 3 ; plate 23, fig. 2 



Description. Small sized nautilicone, composed of three slender 

 but little involute volutions, the last of which becomes slightly un- 

 coiled. Diameter of conch about 100 mm. Volutions in early stages 

 subcircular, in ephebic and gerontic stages compressed elliptical, with 

 subequally narrow abdomen and dorsal sides. Ratio of hight of 

 volution to its width in the third volution as 8:7. Ventral zone 

 little developed, impressed zone a slight flattening, appearing from 

 the second whorl onward. Rate of growth of conch rapid, the hight 

 increasing to double size within one volution. Umbilical perforation 

 large. Living chamber free in gerontic age, its relative length not 

 known. Aperture not observed. 



Cameras very shallow, attaining but an average depth of 3 mm in 

 the ephebic stage. Septa slightly concave ; their depth 4 mm in the 

 last volution ; sutures nearly straight in the dorsal half of the lateral 

 side and strongly bending forward in the ventral half; apparently 

 without any ventral saddle in the ephebic stage. Siphuncle tubular, 

 small (3 mm in the ephebic conch, which has a diameter of 25 mm) 

 propioventran in position in the last whorl, a little nearer to the cen- 

 ter in the earlier volutions, but nowhere centren. Shell smooth. 



