PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



291 



by Miller in 1831, introduced by him to tlie scientific world in 1839, and named 

 Pterickthys by Agassiz in 1840. 



The author then proceeded to oflfer some critical remarks on several of tjje genera 

 and species which Prof. M'Coy has described from the Old Red Sandstone Chiro- 

 lepis velox, M'Coy, is regarded by him as a good species ; but C. curtus as identical 

 with C. Cummingice, and C. macrocephalus Avith C. Trailln. Cktracanthus gran- 

 dispimis and C. pulverulentus are regarded as good species ; but C. lateralis is 

 referred to C. minor. Diplacanthus gibbus and D. perarmatus are accepted. The 

 substitution of Diplopterax for Diplopterus is not considered necessary. Diplo- 

 pterus gracilis appears to be a variety of D. Agassizii. The occurrence of D. 

 macrolepidotus in Caithness, and the restriction of D. macrocephalus to Lethen- 

 bar and Russia, are regarded as a reason for not accepting Prof. M' Coy's view as 

 to the identity of these two forms. 



Osteolepis arenaius, stated by Prof. M'Coy to occur at Orkney, has been met 

 with only in the Gamrie by Sir Philip. 0. brevis is regarded as a good species, 

 though the apparent breadth of the head has probably been misunderstood. Hugh 

 Miller has well figured and described the cranial anatomy of tliis species in the 

 " Footprints." Triplopterus Pollexfeni is also considered to be well established 

 generically and specifically. Sir Philip coincides with Prof M'Coy in classing 

 Dipterus with the Ccelacanthi, but observes that it is distinct from Glyptolepyis. 

 Dipterus has but one anal fin. JJiptems braclxypygopterus and D. macropygopierus 

 are, in the author's opinion, synonyms ; but D. Valencknnesi is regarded by him as 

 distinct. 



Conchodus is esteemed by the author only a provisional genus. 



Sir Philip agrees with M'Coy in separating from the Holoptychius the large 

 fishes of the coal-measures which have received the name Rhizodus from Prof. 

 Owen. The latter have ossified vertebral columns. Holoptychius has decidedly two 

 dorsal fins. Some good specimens lately obtained at Dura Den prove that H. 

 Andersoni and H. Flemingii are specifically the same. The determination of H. 

 princeps by scales alone is not regarded as satisfactory ; but JI. Sedgwickii is a 

 good species. Gyroptychius angustus and G. diplopteroides are considered as good 

 species of a new and important genus ; but Su- Philip refers them to the Sauro- 

 dipteridce, not to the Ccelacanthi. Platygnathus Jamicsoni, Ag., is well founded, 

 as proved by recent discoveries in Dura Den ; but the specimen of jaw named P. 

 paucidens by Agassiz is assigned to Asterolepis by Hugh Miller. 



With regard to the Placodcrmata of M'Coy, Pterichthys and Coccosteus are the 

 types, and Chelyophorus is probably a member of the family ; but it is still doubtful 

 whether Asterolepis and Heterosteus belong to it. CephaZaspis, Pteraspis, and 

 Auchenaspis remain for the limited Cephalaspidce. 



Pterichthys had certainly one dorsal and two ventral fins. 



Sir Philip remarks that in Coccosteus M'Coy and others have mistaken for 

 vertebral centres the thick lower extremities of the neurapophyses ; hence the C. 

 microspondylus of M'Coy is a misnomer, and what he terms the " dermal bones of 

 the dorsal fin reversed," in his specimen, are the haemapophyses. Sir Philip thinks 

 that C. microspondylus and C. trigonaspis must be regarded as synonyms of C. 

 decipiens, Ag. C. pusillus is quoted as a good species, and probably the same as 

 one subsequently described by H . Miller as G. minor. 



In a supplement to this memoir Sir P. Egerton gives several extracts from un- 

 published letters by the late Hugh Miller, descriptive of structural characters of 

 the Coccosteus. Among these notes is the description of a small well-defined 

 Coccosteus which Sir Philip proposes to signalize as C. Milleri. [Drawings and 

 casts, prepared by the late Mr. H. Miller, illustrated these supplemental notes.] 



2. "On the Yellow Sandstone of Dm^a Den and its Fossil Fishes." By the 

 Rev. John Anderson, D.D., F.G.S. &c. 



In his geological remarks on Dura Den, the author described the sedimentary 

 strata in the vicinity as consisting of (in ascending order). — 1. Grey sandstone, the 

 equivalent of the Carmylie and Forfarshire flagstones, with Cephalaspis and 

 Pterygotus. 2. The red and mottled beds, such as those of the Carse of Gowrie, 

 and the Clashbinnie zone with Holoptychius nobilissimus, Phylloltpis concentricus, 

 and Glyptolepis elegaais. 3. Conglomerates, marls, and comstone, with few and 



