18 PALAEONTOLOGY OP THE UPPER MISSOURI. 



tudinally oval scars of the adductors, and outside of these the scars left by the 

 cardinal muscles. 



Some difference of opinion exists in regard to the particular species that should 

 be considered the type of this genus. Most authors have fallen into the habit 

 of viewing Spirifer striatus as the type, mainly, we believe, because Sowerby first 

 discovered internal spiral appendages in that species, and had announced this dis- 

 covery before the Linnsean Society in a paper read in 1814, but not published until 

 during the following year, about the time the second volume of his Mineral Con- 

 chology, containing his description of the genus Spirifer, issued from the press. It 

 is worthy of note, however, that he does not propose, in this paper, to establish a 

 new genus upon Spirifer striatus (which he there designates by the old name 

 Anomia striata) nor upon any other species, though he does allude to Spirifcr 

 cuspidatus, in a foot-note, appended some time between the reading and publication 

 of the paper, as being figured in his Mineral Conchology as " Spirifer cuspidatus" 

 So that even admitting that this paper was distributed a few months earlier than 

 the second volume of his Mineral Conchology, Spirifer cuspidatus would still be 

 the first species in connection with which we have any evidence he ever .used the 

 name Spirifer. It is also the first and only species described by him at the time 

 that he founded the genus in the second volume of his Mineral Conchology, while 

 he there makes no allusion whatever to the species striatus. It has been objected, 

 however, that he admits in his remarks after the description of S. cuspidatus, 

 immediately following the description of the genus Spirifer, that he only inferred 

 from analogy, that this species possessed internal spires. In this inference, how- 

 ever, later discoveries show that he was correct; so that the name Spirifer, as well 

 as all the characters mentioned in his description of the genus, arc as applicable to 

 S. cuspidatus, as to the species striatus. Hence we think that in accordance with 

 the laws of priority S. cuspidatus should be regarded as the type of the genus. 



We are not, however, in favor of so rigidly carrying out this rule as to invariably, 

 and under all circumstances, regard the first species mentioned or described in con- 

 nection with a new generic name, as its type, especially when that particular 

 species may happen to present some important characters directly opposed to those 

 given in the generic description, while another species described at the same time 

 does exhibit these particular characters. But when an author describes a new 

 genus, and at the same time describes but a single species, which presents all the 

 characters given in the description, although he may have only inferred from 

 analogy that it possessed some particular one of those characters he had not seen, 

 we are compelled to regard that species as the type of the genus. The fact that 

 he may have at some previous time seen this character in another form subse- 

 quently referred by him in another volume to the same genus, as Sowerby did with 

 Spirifer striatus, cannot, we should think, invalidate the claims of the first species 

 (S. cuspidatus') to be regarded as the type. 



If we are right in these conclusions, Dalman's name Cyrtia becomes exactly 

 synonymous with the genus Spirifer, since it was founded for the reception of 

 species possessing precisely the characters of the typical forms of that genus ; while 

 the species usually viewed as typical Spirifers, must form a distinct sub-generic or 



