100 Br. Ivor Thomas — Devonian Fossils from Cornwall. 



the name Calymene Icevis from Brushford (North Devon), Mudstone 

 Bay, Durlstone, Knowle Quarry near Newton Bushel (South Devon) 

 (14, p. 130). Salter questions, however, the occurrence at Mudstone 

 Bay and Durlstone (16, p. 17). 



Mr. Howard Fox has collected the same species from Trevone Bay, 

 Cornwall (4, p. 543), and forms doubtfully referred to Icevis from Cant 

 Hill, St. Minver, Cornwall (3, p. 52; 18, p. 154), and near Porth- 

 missen beach, Cornwall (5, p. 6). 



A poorly preserved specimen of a form which somewhat resembles 

 Phacops [Trimerocephalus) anophthalmus^ Freeh (7, p. 270), has been 

 found by Mr. H. Dewey at Daymer Bay, Cornwall (H. D. Ill, Geol. 

 Surv. Coll.), while Ph. [Trim.) cf. anoplitlialmus was collected by 

 Mr. J. Pringle at the same locality and horizon (Pr. 4733, Geol. Surv. 

 Coll.). Specimens collected by Mr. W. A. E. Ussher at Whiteway 

 Farm, Devonshire, in 1888, were then determined as Phacops 

 cryptophthalmus, Emmrich. A re- examination of one of these speci- 

 mens (22884) justifies its determination as a form closely related to 

 that figured by Gximbel. 



Allorisma concinna, sp. nov. (PL III, Figs. 5 and 6.) 



Description. — This shell is fairly globose, equivalve, very in- 

 equilateral, and is much produced posteriorly, the posterior portion, 

 measured from the intersection of the axes, being about twice the 

 length of the anterior. The angular umbones lie far forward, and 

 bend over prominently above the hinge-line. The hinge-line is 

 straight posteriorly, but curves slightly downwards in front of the 

 umbones. Behind and under the umbones lies a small, elongated, 

 narrow ligamental area, gradually tapering posteriorly. A low keel 

 runs from behind the umbo towards the posterior margin of the valve, 

 and is separated from the hinge-line by a narrow, almost smooth, 

 groove, gradually flattening and widening posteriorly. A very obtuse 

 and indistinct keel or fold passes forward from the umbo to the antero- 

 ventral margin. The ornamentation consists of prominent, sub- 

 concentric, regular ridges, lessening in number and lying further apart 

 towards the ventral margin. The ridges commeuce indistinctly 

 anteriorly to the umbo, and after a regular curvature round the 

 obtuse anterior fold run in shallow curves towards the posterior 

 hinge-line. They become indistinct at the low posterior heel. Under 

 a strong lens the best preserved portions of the shell exhibit finer 

 reticulate ornamentation, the components of which are respectively 

 concurrent with and approximately at right angles to the stronger 

 ridges. No traces of internal parts are to be seen. 



Dimensions. — Length, 13'5mm. approx. 



Height, measured at the umbo, 7'5 mm. 



Locality and horizon. — The same as for the above-described species. 



Remarlis. — Some little variation is exhibited in the specimens 

 obtained, though these points do not seem to suffice for specific 

 distinction. Thus, two examples [C.R. 1521, 1672] show 

 irregularity in their ornamentation, one ridge occasionally dividing 

 locally into two parts. One of these specimens [C.R. 1521] alsa 

 possesses more ridges within the same space than the typical form. 



