566 Notices of Memoirs — Fritsch's Elasmobranch Fishes. 



Wiltshire, and the Lithographic Stone of Bavaria. A new fish allied 

 to Semionotus, but with thinner, much imbricating scales, is also 

 conspicuous ; and another new form, allied to the Dapedioids, is 

 remarkable from the presence of typical rhombic ganoid scales in 

 the front half of the trunk and deeply overlapping cycloid scales 

 over the whole of the caudal region. A Leptolepis-lils.e fish, with 

 a persistent notochord, seems to represent a third unknown generic 

 type. Of Leptolepis itself there are many hundreds of individuals 

 in a fine state of preservation. The fishes occur in a hard, ferru- 

 ginous, fissile matrix, associated with well-preserved remains of 

 plants. 



V. — A Sketch of the Geology of Devonshire. By Townshend 

 M. Hall, F.G.S. [Third edition, 1890. Keprinted from White's 

 History, etc., of the County.] 



IN the Geological Magazine for August, 1879, we briefly drew 

 attention to the first edition of this article, which gives a capital 

 condensed account of Devonshire Geology. In the present edition 

 the results of recent rescearches are noticed, and some accounts of 

 the Mines and Mining are added. We observe, however, that the 

 Bovey beds are classed as Miocene, and nothing is said of Mr. Starkie 

 Gardner's contention that the beds are of Eocene a^e. 



VI. — Preliminary Notes on the Paleozoic Elasmobranchs, 

 Pi eur acanthus and Xenacanthus, from the Lower Permian of 

 Bohemia. By Dr. Anton Fritsch. 1 



THE next part of the author's work, " Fauna der Gaskohle," 

 which will probably appear before the close of the present 

 year, is devoted to further investigations upon Pleur acanthus and 

 Xenacanthus. Bestored figures, first exhibited to the British 

 Association at the Leeds Meeting, have been carefully prepared, 

 being based upon the examination of no less than 200 specimens. 

 The principal result arrived at is, that the three genera, Orthacanthus, 

 PJ eur acanthus, and Xenacanthus, are well characterized, and are all 

 true Selachians. The skull is developed as a simple embryonic 

 capsule, showing no ossifications or separate bones : it much 

 resembles that of Heptanchus, and indicates that the thi-ee genera 

 in question also belong to the Opistharthri of Gill. The branchial 

 arches are likewise seven in number, as in Heptanchus. The 

 median fins are embryonic in character, much like those of deep- 

 sea Gadoids (e.g. Bathygadus). The pectoral fins are of the most 

 primitive type in Orthacanthus, more advanced in Xenacanthus, and 

 still more resembling the abbreviated fins of recent sharks in 

 PI eur acanthus. There is no pelvic element, the basal part of the 

 pelvic fin of each side being merely a fused mass of parallel cartila- 

 ginous rays. The claspers in the male closely resemble those of 

 modern sharks, being formed by a modification of the dorsal or 

 postaxial rays. 2 In the vertebral column, intercalaria are developed 

 both in Orthacanthus and Xenacanthus. 



1 Abstract of paper read before Section C, British Association, Leeds, 1890. 



2 See figure in Zool. Anzeiger, No. 337 (1890). 



