490 
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 Z. 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, z. ¢., 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. 
ZT. planorbiformis, sp. Hall, may be distinct from Z: ammonius, 
since the name has been adopted by Hall, who has studied the type, 
and this may be the same as 7: planorbiformis, Conrad. 
TROCHOLITES BLAKEI. 
TROCHOLITES PLANORBIFORMIS, Blake (British Ceph., Pl. xxix, 
Fig. 9). 
This species, considered by Blake as identical with A/anorbifor- 
mis Conrad, is obviously a distinct form. It has deep ventral lobes 
in the sutures and costz 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 Zztuztes 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 sey- 
eral species confused under this one name. 
It occurs in the Bala beds at Llandovery. 
‘TROCHOLITES ANGUIFORMIS. 
NavTiLus (TROCH.) ANGUIFORMIS, Blake (Brit. Ceph., Pl. xxvii, 
Hig) 2). 
This is also a true member of this genus. 
* Murchison’s Siluria, p. 220, Fig. 8. 
