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Dr. C. Rominger has kindly sent to me a fossil from the 

 Hamilton shale, of Thunder Bay, Michigan, in which the 

 terebratuloid loop is distinctly visible. The form of 

 the shell is ovate, not very unlike Cryptonella, but 

 more rotund, the lateral edges more incurved, and the space 

 below the beak of the ventral valve not so great, nor the 

 deltidial plates so conspicuous as in species of that genus, 

 On a critical examination of the interior, after cutting 

 away the crystalline rilling of the shell nearly to the loop. 

 I am unable to find any difference between it and true 

 Terebratula ; and we have, so far as I know, for the first 

 time the positive determination of this genus in our De- 

 vonian rocks. The position and proportions of the loop 

 are shown in fig. 22, which is an outline of the shell from 

 the dorsal side, twice enlarged. Fig. 23 is an enlargement 

 of the loop, showing the crural processes. 



Fig. 22. Fig. 23. 



Figures 22 and 23, Illustrations of Terebratula romingeri, Winchell. 



At the same time, Dr. Rominger has also sent me speci- 

 mens of Terebratula melonica of Barrande, one of which he 

 has prepared so as to show in a very satisfactory manner 

 the loop in its entire extent. The specimens correspond 

 with those I have received from M. de Verneuil under the 

 same name, and therefore we must regard them as authen- 

 tic. The external form of T. melonica is not unlike some 

 of the less gibbous forms of Cryptonella, and is much less 

 gibbous than the usual forms of Waldheimia. The lamel- 

 lae are nearly parallel and near together, and the loop is ex- 

 tended four-fifths the entire length of the shell, when it is 



