419 PALEONTOLOGY OF NEW-YORK. 



ADDENDA. 



Trematospira? iiobilis. 



PLATE. 



Rhynchotpira nobilU ; Hah, Thirteenth Report on the State Cabinet, p. 83. 1860. 



This species was omitted iu its proper place, in the hope of being able 

 to determine its true relations ; but the result has not been quite satis- 

 factory. It appears, however, to be more nearly related to the Genus 

 Trematospiea than to Rhynchospira ; and it may be found to differ from 

 either of these when the internal characters shall be fully ascertained. 

 Shell large, broadly subovoid; surface plicated. 

 Ventral valve with a broad mesial sinus ; the beak large and truncated 



by a large round foramen, the lower side of which is bounded by the 



summits of the deltidial plates : margins of the valve subalate a little 



below the beak» 

 Dorsal valve the more gibbousj'with a broad, moderately elevated mesial 



fold. 

 Surface marked by numerous angular elevated plications, which are 



sharply crenulated on the summits ; the sides and intermediate spaces 



finely and evenly striated. On the mesial fold there are from nine to 



eleven plications, and a corresponding number in the sinus. 



The interior of the ventral valve shows a strong tooth on each side 

 at the base of the fissure ; the rostral cavity is limited by a callosity, 

 and the muscular area is strongly marked and somewhat quadrate in 

 form, as far as observed. 



The interior of the dorsal valve shows strong crural processes exten- 

 ding from the hinge-line for a short distance, when they become slender 

 and flattened ; and below this they curve and send ofi" a process towards 

 the centre of the shell, as in others of the genus, and similar to that of 

 Terebratula. 



Geological formation and locality. Iu the Hamilton group ; at Darien, Genesee 

 county, New- York. 



