NOTICE OF PALJEONTOLOGY OF NEW YORK. 179 



In tlie Hamilton group, the most abundant and widely distributed 

 species is Sjnrifem mucronata. In the same group are the following : 



8j)irifera tullia (n. s.), 



8. 



formosa, 



8. 



sculptilis, 



8. 



ziczac, 



8. 



granulifera 



8. 



marcyi, 



Spirifera medialis, 



8. medialis var. eatoni, 



8. angusta, 



8. maci^onata, 



8. subumbona. 



Spinfera acuminata and S. fimhriata recur in this group ; the latter is 

 not uncommon. 



Several species heretofore described are indicated as doubtful, requiring 

 further material and investigation. 



The Portage group has furnished only the Spirifera loevis ; which has 

 much the general aspect of a Carboniferous form. 



In the Chemung group, we have : 



Spinfera mesacostalis, 

 8. mesastrialis, 



8. disjuncta, with its numerous synonyms and the species repre- 



sented in a great variety of aspects; 

 8. alta (n. s.), 



8. proematura (n. s.). 



The chapter on Spirifera is concluded with some remarks upon the 

 geological and geographical distribution of the species of Spirifers, the 

 hinge-structure, etc. ; which have already been published. 



The name Amboccelia is continued, being regarded as presenting 

 sufficient distinction from Spirifera; and in the Hamilton group are 

 recognized : 



Artibocddia umhonata, 

 A.. preambona. 



In the Chemung group, A. umhonata var. gregaria. 



On page 263 of the volume are some observations on the Genus 

 Cyrtia of Dalman, and Cyrtina of Davidson. 



So long since as in 1858, Mr. Davidson, in his Introduction to the 

 Study of the Brachiopoda, had expressed some doubts as to the value of 

 the Genus Cyrtia of Dalman ; and later investigation had shown that 

 the typical species of that genus does not differ from Spirifera. At the 

 same time, some forms usually referred to the Genus Cyrtia possess a 

 peculiar modification of the dental plates, with a largely developed 

 median septum and punctate structure of the shell. For these forms. 



