DESCBIPTIONS OF SPECIES. 289 



nized by Hail and Clarke. It can evidently not be grouped with the radiati nor 

 with the lamellosi, nor yet with the great group of the aperturati, while the 

 (jlabrati, are too unlike in every waj^ to requii'e consideration. However, this shell 

 seems to show a certain parallel development in internal structure with Martiniopsis 

 of the glabratl, as in that genus both valves possess dental lamellse. With the 

 ostiol'atl many points of similarity exist. "'Many of the middle Devonian repre- 

 sentatives," say Hall and Clai-ke, " "bear a low, median sulcus on the fold, which 

 may be accompanied by a broad, very faint, indistinct plication apparent only near 

 the anterior of the sinus." Some species have the plications covered with elongate 

 pustules {8p. grmiulosua and Sp. marcyi) or erect granules {Sp. asper), and in Sp. 

 parryamis the minute elongate pustules are arranged upon the summits of distinct, 

 fine, radial strife (Hall and Clarke). Another character, which is frequently met 

 with in this group, is the callosity developed in the apex of the delthyrium. 



In general configuration the form under discussion agrees with the ostiolati 

 even to the extent of showing a median groove on the fold and a cori-esponding 

 elevation in the sinus, but the ostiolati are characteristically' large and stout shells, 

 while this is a very small one. 



The surface ornamentation may be conceived to be the same, but after examining 

 the surface of a number of the ostiolate spirifers, I am led to believe that the granules 

 or pustules are related to the superficial layers of the shell and ai"e solid, while in 

 the form under comparison they are believed to be hollow. In this form the cal- 

 losity chai'acteristic of the ostiolati, is not known to occur, nor, 1 believe, are there 

 found \n the ostiolati the dental lamellae which seem to be a constant feature of its 

 internal structure. The evidence, therefore, seems on the whole to separate this 

 form from the ostiolati. Its aflinities are, indeed, possibly closer with the fim- 

 lyi'iati than with any other group. If mj' conclusions regarding the character of its 

 surface tally with fact, namely, that the spines are simple and hollow, it would fall' 

 by reason of this and other characters within the ■imicispinei division of that group. 

 It agrees in its short hinge line, spinose surface, and simple plications with the uni- 

 cispinei, among which certain forms, as for instance 8p. vamcxemi, exhibit a tendency 

 to division in the fold and sinus. Of the two subsections recognized by Hall and 

 Clarke this species belongs undoubtedly to type a, or the crispus type, because of its 

 strong plications. However, the surface of the unicisplnei is closely lamellate, the 

 lamelhv bearing rimbritu of crowded spines, while the sui'face of Spirifer sp. 5 shows 

 no regular concentric lamellae, and, though the spines are in concentric rows, they are 

 inclined to be distributed at regular and comparatively distant intervals. A struc- 

 tural difference of some importance consists in the dental lamellae of the dorsal valve 



a Pal. New York, vol. 8, pt. 2, 1894, p. 29. 



14364— No. 16—03 19 



