104 PALEONTOLOGY OF NEW YORK. 



from tho Paradoxides Beds ; A. subc.onica and A. disparirugata, Kutorga, from 

 the primordial beds of Russia; A. Nicholsoni and A. ? costata, Davidson, from the 

 Llandeilo. The hist species is strongly ribbed on its exterior, but its generic 

 rehations are too uncertain to allow this fact to be regarded as adding a new 

 feature to the genus. 



Genus CONOTRETA, Walcott. 1889 



* 



PLATE IV K, FIGS. IC-21. 

 1889. Conotreta, Walcott. Proceedings National Museum, vol. xii, No. 775 ; Advance Sheet, Dec. 10. 



Diagnosis. The pedicle-valve is conical, its height being greater than its 

 length. The apex is more or less broken on all the specimens, but in a single 

 minute valve from Covington, Kentucky-, there is evidence of the external 

 opening of the sipho. From the apex, a shallow furrow extends to the poste- 

 rior margin, increasing in width downward. In the smaller specimens the 

 posterior wall of the shell conforms to the curvature of the rest of the surface, 

 interrupted only by the longitudinal depression, but, with increase in size, 

 this area becomes distinctly flattened, as in Acrotreta. Surface covered with 

 sharp concentric striae which make a slight upward curve as they cross the fora- 

 minal groove. 



The casts of the interior show a strong apical callosity surrounding the 

 probable position of the foramen. This is somewhat produced anteriorly into 

 a short sharp ridge, on either side of which lie two other ridges, with evidence 

 of a third on the lateral slopes. Upon the largest of the specimens these ridges 

 seem to have been hollowed at their extremities. 



Type, Conotreta Rusti, Walcott. 



* In a preliminary li.st of the genera of the paloBozoic brachiopodn, published in the Eighth Annual 

 Ueporl of the State Geologist, 1S89, p. 4^, the term Gei.vitzt.\ was used for this genus, a ilescription of which 

 hafl at that time been prepared from material in our hands, obtained fi-om the Utica horizon at Covington. 

 Kentncky. It would have been necessary to withdraw this name, as it had already been in use for a genus 

 of fossil plants (K.NDLicHEn, Synop.sis Coniferarum, p. 281. 1847). Meanwhile Mr. Walcott h.'is described 

 the genu.s from specimens from Trenton Falls, in an ailvance sheet of the Proceedings of the N.itional 

 Museum, privately circulated. We have been permitted to make use of his specimens for sl'idy juid 

 illustration. 



