432 Reviews — Lekly's Cretaceous Reptiles, 



It will not be denied, I believe, that these are the principal natural 

 subdivisions of the Ganoids, and that the three great *' series," 

 namely, the Lepidosteidce, Lepidopleuridce, and Crossopteri, are closely 

 related, especially through their more ancient types, and cannot be 

 separated, While I would exclude from the Ganoids all other 

 types, e.g., the Dipnoi (Lepidosiren), Sturionidce, Amides; the Jurassic 

 Teleostei (Leptolepides) Megaluri, Caturi, which are peculiar types 

 or simply tlimilies of the true Teleostei Physostomi; the Hoplopleurides 

 Dercetiformes,^ which are true Teleostei (Physoclysti f) without 

 Ganoidean affinities; the AcantJiodidce, which are, perhaps, better 

 placed with the Selachians ; the Placoderms, and Cephalaspidce 

 (" incert^ sedis "), at least provisionally. I would limit the Ganoids 

 (which I regard only as a peculiar sub-order of the Physostomi) to 

 the three above-named tj^pes, and thus define them : — 



" Every fish of the order Physostomi (comprising those fish which 

 generally have an air tube, abdominal fins, and soft articulated rays) 

 is a Ganoid, which has either the rhomboidal articulating scales of a 

 Lepidosteus ; the interlocked scales, attached to the dermal ribs of a 

 Pycnodont; the "lobate" fins and jugular plates of Sb Polypterus ; 

 or that combines several of these characters." 



IV. — Cretaceous Eeptiles of the United States. 



UNDEK this title Professor Leidy published in 1865, in the Smith- 

 sonian Contributions to Knowledge, a monograph of the species 

 of Eeptiles then known, from the strata usually called Cretaceous, in 

 New Jersey, Nebraska, Missouri, and other localities in the United 

 States. 



It makes known by 120 pages of letterpress and 20 plates, a fauna 

 of 28 species, eight of which find their names in the concluding 

 synopsis : the table of contents enumerates 20 species. Ten of the 

 28 species find their descriptions here for the first time, and 20 of the 

 species appear to have been first named by Professor Leidy. He 

 states that he has been occupied on the monograph for seven years, 

 and if the result should appear to be slight, we can well understand 

 the difficulty of determining species with the conscientious desire for 

 accuracy which the Professor displays, from the fragmentary 

 materials athis command. Two genera (Mosasaurus and Hadrosaurus) 

 occupy 70 pages, while several, founded on teeth, are rapidly dismissed ; 

 svLchsiYeAstrodon, Tomodon, PUogonodon, Polygonodon, Trachodon, Pirato- 

 saurus. Polygonodon presents the fonn of Saurocephalus, for which 



of Ccelaeanthini, that I have just now been fortunate enough to procure, should be 

 added the Triassic Graphiurus of Kner, who will give us some information on the 

 Eoplopygus of Agassiz, that appears also to belong to this family (or of the Gyrosteus, 

 said to be related to Chondrosteus, Eg.). Descriptions of several species of Undina 

 that have escaped the attentive care of Prof. Huxley will be found in Wagner's and 

 ThroUicre's descriptions of the fishes of the lithographic slates of Bavaria and France. 

 ' This sin gidar family is noticed in Pictet and Humbert's " Poissons fossiles du 

 Liban." It is very characteristic of the Cretaceous period. I would nevertheless 

 propose to unite with it the Triassic genera Belonorhynchus and Ichthyorhynchus^ the 

 oldest known (not Ganoidean) Teleostei, 



