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nius or circularis and the involution of the whorl, although not 

 distinctly seen, is also apparently greater. 



Trocholitus minusculus, Mill, et Dyer, is a small species having 

 such extraordinary sutures that one suspects some distortion, never- 

 theless there is no proof of any action that would have brought 

 this to pass. The form, except the size, is like that of T. ammonius. 

 The incomplete living chamber is somewhat less than one-half of a 

 volution in length. The sutures have flexures like those of the 

 lines of growth in other forms, /. e., they form a deep, broad sinus 

 on the venter, rise into prominent saddles on the sides which inter- 

 nally sink towards the lines of involution, probably forming a 

 lobe in the contact furrow. These outlines are unique among the 

 species of Trocholites. The shell is shown on part of another 

 specimen, and the hyponomic sinus in the lines of growth on the 

 venter is narrower than the ventral lobe of the sutures. 



T. planorbiformis, sp. Hall, may be distinct from T. ammonius, 

 since the name has been adopted by Hall, who has studied the type, 

 and this may be the same as T. planorbiformis, Conrad. 



Trocholites Blakei. 



Trocholites planorbiformis, Blake {British CeJ>h., PL xxix, 

 Fig- 9)- 



This species, considered by Blake as identical with planorbifor- 

 mis Conrad, is obviously a distinct form. It has deep ventral lobes 

 in the sutures and costse which are figured on either side of the ab- 

 domen. No longitudinal ridges are described, although the surface 

 was studied and the transverse markings were plainly seen. 



Blake states that this is identical with Lituites hibernicus, Salter,* 

 but the latter is a ribbed species with part of the whorls free and 

 does not even belong to the same family. There are probably sev- 

 eral species confused under this one name. 



It occurs in the Bala beds at Llandovery. 



Trocholites anguiformis. 



Nautilus (Troch.) anguiformis, Blake {Brit. Ceph., PL xxviii, 

 Fig. 2). 



This is also a true member of this genus. 



* Murckison's SUuria, p. 220, Fig. 3. 



