104 PALEONTOLOGY OF NEW YORK. 



from the Paradoxides Beds ; A. subconica and A. disparirugata, Kutorga, from 

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

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

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

 feature to the genus. 



Genus CONOTRETA, Walcott. 1889* 



PLATE IVk, figs. 16-21. 

 1889. Conotreta, WALCorr. Pi-oceedings 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 strias 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 list of the genera of the palaeozoic brachiopoda, published in the Eighth Annual 

 Report of the State Geologist, 1889, p. 43, the term Gkwitzia was used for this genus, a description of which 

 had at that time been prepared from material in our hands, obtained from the Utica horizon at Covington, 

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

 of fossil plants (Endlichek, Synopsis Coniferarum, p. 281. 1847). Meanwhile Mr. Walcott has desci-ibed 

 the genus from specimens from Ti-enton Falls, in an advance sheet of the Proceedings of the National 

 Museum, privately circulated. We have been permitted to make use of his specimens for study and 

 illusti'ation. 



