92 Scientific Intelligence. 



logical research has been tactfully overcome, viz., the question 

 when an author should turn from the work of investigation and 

 take the scientific public into his confidence. 



From the occurrence of considerably specialized ichthj^osaurs 

 in the middle Triassic of regions as widely separated as Europe 

 and western North America, it is argued that these forms had 

 long been in existence as a marine tj^pe. Thus in the division of 

 the memoir on general skeletal structure, the skull of Cymbo- 

 spondylus, from the middle Triassic of West Humboldt Range in 

 Nevada, is shown to be "the product of an ancestry which had 

 expressed this special type of aquatic adaptation for a long 

 period." In this connection it is interesting to learn that Cym- 

 bosjjondylus is still the only Triassic ichthyosaurian genus 

 represented by a well-preserved skull. In the known Triassic 

 forms the number of presacral vertebrae is proved to be generally 

 larger than in the typical Ichthyosaurus. This is slightly dis- 

 turbing to the view held by some paleontologists that the 

 Phytosauria are ancestral to the Ichthyosauria; and there are, the 

 author states, a number of other characters apparently indicating 

 that these two groups have arisen independently of each other. 

 The principal points of difference between the Triassic and the 

 Jurassic ichthyosaurs are arranged in parallel columns so as to 

 demonstrate that the characteristics of the earlier genera are 

 practically all nearer to those of land or shore animals, while 

 " the characteristics of the later genera take the direction of 

 specialization toward an adapted fish-like form." Yet on the 

 whole, this evolution from a semi-aquatic reptilian type to one 

 better fitted for life in deep water has been extremely gradual, 

 and the unity of the Ichthyosauria (here divided into the families 

 Mixosauridae and Ichthyosauridae) can not be questioned. At 

 precisely what geological period the "unknown crawling ances- 

 tor" of the ichthyosaurs asserted its independence from the 

 parent shore-type, PrOf. Merriam wisely does not state ; but he 

 places this event not later than the early part of the Trias — 

 possibly at an even earlier period. The text-figures and plates 

 are excellent ; and a carefully prepared index adds greatly to the 

 value of the work. g. f. e. 



14. Catalogue of the Type and Figured Specimens of Fossil 

 Vertebrates in the American Museum of Natural History, Part 

 I— Fishes ; by L. Hussakof, Bull. Amer. Mus. Nat. Hist., Yol. 

 xxv, pp. 1-103, with one diagram and plates i-vi, June, 1908. — 

 In this exhaustive catalogue not only are all of the primary and 

 secondary types of fossil fishes in the American Museum enumer- 

 ated, but the condition of the specimen, together with the literary 

 reference of the original description, or descriptions, is given. In 

 all 49 text-figures are printed, while a number of specimens, mainly 

 the types of Cope and Newberry, are illustrated in the excellent 

 plates. The diagram gives in tabular form the classification and 

 geological summary of the 562 types included in the catalogue, 



R. S. L. 



