COCHLIODONXIDJE. 
183 
under the name of Helodus dentatus , H. Bomanowsky, 
Bull. Soc. Imp. Xat. Moseou, 1864, pt. ii. p. 159, pi. iii. 
fig. 15. Baugh Coll. 
42187. T wo smaller but similar dental plates; Oreton. Baugh Coll. 
Psephodus dubius, sp. nov. 
Type. “ Lower ” dental plate shown in PI. VI. figs. 13, 13 a. 
The provisional name of P. dubius may be given to a species 
indicated by the large dental plate shown in the figure. This 
specimen corresponds most closely in its characters and dimensions 
to the “ lower ” dental plate of P. magnus, exhibiting a similar 
coronal contour and coarsely crimped borders, but having a rela¬ 
tively much less antero-posterior measurement, and*the outer portion 
of the plate not being so abruptly truncated but prolonged into an 
inroiled point. In addition to this gradual inrolment the plate 
is sharply bent along an oblique transverse line about its middle, 
and the marks of wear appear to be confined to the area outside this 
fiexure. 
Form. $ Log. Carboniferous Limestone: Shropshire. 
P. 4209. Typ e-specimen ; Oreton. Enniskillen Coll. 
42183. A broken specimen, showing the considerable thickness of 
the dental plate, and faint transverse sutures near its 
inner margin; Oreton. Baugh Coll. 
P. 227 a. Smaller dental plate, much w r orn, showing the inrolment 
of the outer apex, and transverse sutural lines across the 
crown near its inner margin; profile outline restored in 
PL VI. fig. 13 a; Oreton. Weaver-Jones Coll. 
42191-93. Three small dental plates of similar form, either per¬ 
taining to young of this species, or, if the so-called 
“ lower ” dental plates of P. salopiensis prove to be erro¬ 
neously identified above, perhaps referable to the latter ; 
Oreton. Baugh Coll. 
P. 227 b. Small “ upper ” dental plate, having an antero-posterior 
measurement of (P016, and, so far as preserved, very 
similar in form to the corresponding dental plate of 
P. magnus; it is shown of the natural size in PI. VI. 
fig. 12, and may possibly be referable to this species ; 
Oreton. Weaver-Jones Coll. 
Two undetermined species of Psephudus, remarkable for the rela- 
