104 PALEONTOLOGY OF NEW YORK. 



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

 the primordial heds of Russia ; A. Nicholsimi and A. ? costala, Davidson, from the 

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

 rehxtions are too micertain to allow this fact to be regarded as adding a new 

 feature to the genus. 



Genus CONOTRETA, Walcott. 1889.* 



PLATE IV K, FIOS. 16-21. 

 1889. Conotreta, Walcott. Proi^eeciings National Museum, vol. xii, No. 77i5 ; Advaiu^e 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 siplio. From the apex, a shallow furrow extends to the poste- 

 rior margin, increasing in widtli 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 liave been hollowed at their extremities. 



Type, Conotreta Rusti, Walcott. 



* In a preliminaiy list of the genera of the luilaeozoio l)i-achiopoda, iniblished in the Eighth Annual 

 Report of tlje Stale Geologist, 1889, p. 4;i, the tei-iii (ikinitzia was used for this genus, a description of which 

 had at that time been pi-epared from material in our hands, obtained from the Utica horizon at Coving-ton. 

 Kentucky. It would have been neces.sary to with(h-aw this name, as it had already been in use for a genus 

 of fossil plants (E.NnLicuEK, Synopsis Coniferaruin, p. 281. 1847). Me.anwhile Mr. Walcott has described 

 the genus from specimens from Trenton Falls, in an advance sheet of the Proceedings of the National 

 Museum, privately cin-ulated. We have been jwrmitted to make use of his .specimens fin- study and 

 illusti-ation. 



