28 Notices of Memoirs—Rer. G. F. Whidborne—Devonian Fossils. 
there is scarcely any posterior area, the two rows of marginal denticles 
being placed close to each other and alternating. As the spine 
increases in length, the ridges begin to drop off behind, so that in 
examples of from three to four inches in length, like Agassiz’s type,’ 
only the tip is ridged all round, while three ridges, one median and 
two lateral, persist beyond the other along the front, whence the 
name Tristychius. Along with this change in sculpture, the two 
posterior rows of denticles diverge from each other, and a well- 
marked area is formed between them as in Cienacanthus. 
In still larger spines the sulcated tips become entirely worn off, 
leaving only the three anterior ridges, which in turn also finally 
disappear in examples which have been subjected to any consider- 
able amount of wearing. A somewhat short, gently-curved, bluntly- 
pointed spine now contronts us, destitute of ridges or sulci, and with 
the surface covered only by very close and delicate striz. Such 
spines are indistinguishable from Agassiz’s description and figure of 
Piychacanthus sublevis,? of which the original seems unfortunately 
to be lost, for although Agassiz states that it belonged to Professor 
Jameson, I have never been able to find it in the Edinburgh Museum. 
Ptychacanthus sublevis then represents to my mind nothing but 
an adult Tristychius arcuatus, with the point broken off, and the 
general surface a little worn, and this view is, I consider, not only 
corroborated, but proved by a series of specimens of undoubted 
Tristychius in the Edinburgh Museum. 
INj@ i EC Swern Vir VE@ dees: 
].—AMeBLyYprisTIs CHOPS, NOV. GEN. ET. SP., AUS DEM HocAEN 
Axneyprens. By Prof. Dr. W. Dames. Sitzungsb. Ges. naturf. 
Fr. Berlin, 1888, No. 6. 
HIS paper forms an interesting contribution to our knowledge of 
the fossil vertebrate fauna of Birket-el-Qurin, in Fajum, for which 
we are already indebted to Dr. Dames (Sitzungsb. konigl. Akad. 
Wiss. Berlin, 18838, pt. i.). The evidence of the new Saw-fish 
(Amblypristis Cheops) consistsin some detached rostral teeth, differing 
from those of the existing Pristisin their shortness and great relative 
breadth. One example is figured; and Dr. Hilgendorf adds a brief 
note on the structure of the rostral teeth of the living genus, as 
compared with the fossil. 
I].—Own some Devontan Crustacea. By Rev. G. F. Warpsorne, 
M.A., F.G.S.3 
ESIDE species of Crustaceans already described from Woul- 
borough and Lummaton, several new species are found there, 
as the following : Phacops batracheus, which differs from P. fecundus, 
Barr., in the rearward position of the eye and more overhanging 
glabella; Proetus batillus, which has a flatter glabella than P. 
1 Poiss. Foss, tome iii. tab. 1a, fig. 9-11, 
? Op. cit. tome iii, tab. 5, fig. 1-3. 
3 Revised abstract of paper read at the British Association. 
