NOTICE OF PALEONTOLOGY OF NEW-YORK, VOLUME IV.' 149 



and, waning during the Permian epoch, is presented for the most part in 

 degenerate modifications of the typical forms. Although we cannot shut our 

 eyes to this fact of development to what may be termed the perfection of 

 the type, and its more abrupt decline, we are either compelled to extend 

 the characters of Productus so as to cover the two forms or modifications 

 indicated, or else to propose a distinct designation. The latter course has 

 been adopted, and the name Productella is proposed for the strophaloid 

 Productids of the Devonian period. 



The Subgenus Productella is compared as follows, in Pal. N. Y., 

 Vol. IV, page 153 : 



" These shells difi"er from Strophalosta in the extremely narrow linear 

 cardinal area, greater extension of the hinge-line, more extreme arcuation 

 or ventricosity of the ventral valve in many or most of the species, and 

 especially in the direction and termination of the reniform vascular impres- 

 sions, which resemble those of Aulosteges and of some species of Pro- 

 ductus. It differs from Productus in the constant presence of an area, 

 hinge-teeth and sockets." 



Under this genus are enumerated and described, from the Upper Helder- 

 berg and Hamilton groups, the following species : 



Productella suhaculeata, 



P. 



dumosa^ 



P. ■ navicella, 



P. 



exanthemata^ 



P, shuviardianQy 



P. 



tullia (n. s.), 



P. spinulicosta, 



P. 



subalata. 



P. truncatay 







From the Chemung group, we have : 



Productella hirsuta, 



P. 



P. hirsuta var. rectispina, 



P. 



P. boydii, 



P. 



P. rarispina, 



P. 



P, lachrymosa, 



P. 



P. lachrymosa var. limay 



P. 



P. lachrymosa var. stigmata, 



P. 



P. s^eciosa 





striatula (n.s.), 

 hystricula (n. s.), 

 costatula (n. s.), 

 costatula var. strigata, 

 arctirostrata, 

 bialveata (n. s.), 

 onusta (n. s.). 



So great a number of fossils of this type, in many localities, and par- 

 ticularly in the western part of the State, give a carboniferous aspect to the 

 strata ; and leaving out a few forms which gradually disappear in the wes- 

 tern extension of the formation, the palaeozoic evidence might be regarded 

 as decidedly favoring this view. The distinction, however, between Devonian 

 and Carboniferous faunas is based as often upon geographical as chronologi- 

 cal relations. 



