belonging to the Class Palliobranchiata. 33 



the smooth and the plicated Terebratulas*. Afterwards M. von 

 Buch, in his memoir ' Uber die Terebrateln/ on account of the 

 same difference, divided them into the two divisions " Plicata " 

 and " Non-plicata." Still later, Professor Phillips, in his ' Pa- 

 laeozoic Possils of Cornwall/ &c, elevated the Terebratulas to the 

 rank of a family under the name Cyclothyrida, which includes 

 two genera, Epithyris and Hypothyris, the former having the 

 "beak truncate, perforate," and the latter the "beak acute, the 

 perforation below it i" Hypothyris agrees with the plicated and 

 Epithyris with the non-plicated divisions of Sowerby and Von 

 Buch. More recently, Mr. M'Coy, in the ' Synopsis of the Moun- 

 tain Limestone Possils of Ireland/ has divided the family Tere- 

 bratulidce into five genera, Atrypa, Semiluna, Delthyridtea, Cyclo- 

 thyris and Terebratula : the last two only merit our attention at 

 present, as they correspond with the genera proposed by Professor 

 Phillips. In the same year that Mr. M 'Coy's observations ap- 

 peared, Dr. Carpenter, at the York Meeting of the British Asso- 

 ciation, read a report a On the Microscopic Structure of Shells," 

 in which the Terebratulas are divided into two sections, the 

 " perforated " and the " non-perforated," that is, with reference to 

 the arrangement of the tissues composing the shell : these sections 

 are also in exact correspondence with the two divisions under 

 consideration f. 



It will now be evident that the Terebratulas, from the year 

 (1815) in which Mr. J. Sowerby's views appeared to the present 

 period, have been grouped under two leading divisions, and that 

 these divisions have been proposed with reference to three sets of 

 characters totally distinct from each other : a stronger proof of 

 the necessity of elevating them to the rank of genera cannot be 

 required. 



Before proceeding further, it will be necessary to make a few 

 remarks on the names which have been proposed for the two 

 genera so clearly established. If we agree to those of Professor 

 Phillips, the old name Terebratula will be expunged from concho- 

 logy : this I am strongly disposed to think will scarcely be sanc- 

 tioned : I am therefore induced to prefer it to the proposed sub- 

 stitute Epithyris. It is now difficult to say whether the name 

 Terebratula was first applied to the smooth or the plicated spe- 



* Mineral Conchology, vol. i. p. 189. 



t There seems to be an error in Dr. Carpenter's list of " non-perforated " 

 species, as it contains Terebratula variabilis (of Sowerby, not of Schlotheim 

 I presume), which, judging of its form, &c, appears to belong to the perfo- 

 rate division : this is in a great measure proved by the fact, that the same 

 shell is represented in the illustrations with a perforate tissue (vide Report 

 of the British Association for 1844, plate 17. lig. 39). Has not a similar 

 mistake occurred with Terebratula subrotunda ? 



Ann. $ Mag. N. Hist. Vol. xviii. D 



