ORDER IV SAUEOPTERYGIA 171 



Family 1. Ichthyosauridae. 

 TFifh the characters of the order. Trias to Cretaceous. 



Jlixosaurm, Baur. Most of the smaller -sized Triassic remains are placed 

 in tliis genus as distinct from Ichthyosaurus, the teeth being in less uniform 

 series, and the limbs less completely paddle-shaped. The radius and ulna are 

 elongated, and separated by an interstice throughout their length. 31. 

 cornalianus, Bassani, the typical species, varies from 0"5 to 1 m. in length, 

 and occurs in the Upper Trias of Besano, Lombardy. M. atavus, Quenstedt, 

 is known by fragments from the Muschelkalk of Wiirtemberg. 



Ichthyosaurus, Konig (Figs. 262-271). Teeth conical and in uniform series. 

 Eadius and ulna shorter than broad, proximally in contact. Humerus and 

 femur with two concave distal facettes. Total length of largest forms upwards 

 of 10 m. 



This genus is most abundant in the Lias, I. communis and I. intermedius being 

 familiar English species. Localities noted for the excellence of their fossil remains are 

 Dorsetshire (Lyme Regis) and Somersetshire in the Lower Lias, and Yorkshire, Cal- 

 vados, "Wurtemberg (Boll, Holzmaden), and Franconia (Banz, Altdorf) in the Upper 

 Lias ; and the species of the one division are for the most part distinct from those of 

 the other. I. comrfiunis, intermedius, latimanus, platyodon, and tenuirostris are 

 especially characteristic of the Lower Lias, and I. acutirostris, ingens, quadricissus, 

 and trigonodon of the upper member. Remains of Ichthyosaurus are sparse in the 

 Middle Jura, but a number of species occur in the Upper Jura of Solenhofen and 

 Kelheim, Bavaria, Northern France, and England. Cretaceous forms are known from 

 England, France, the East Indies, Australia, New Zealand, and Chili. 



Ojyhthalmosaurus, Seeley. Edentulous or with minute teeth confined to 

 front of the jaw. Humerus and femur with prominent trochanteric ridge 

 and with three concave distal facettes ; all remaining limb bones more or less 

 rounded and separated. Clavicles separated. Upper Jura and Lower Creta- 

 ceous ; England. 



Baptanodon, Marsh (Sauranodon, Marsh non Jourdan). Similar to the 

 preceding, but completely edentulous. Interclavicle not observed ; digit 

 arising from the intermedium consisting of two longitudinal rows of ossicles. 

 Coracoids unite in the median line in large elliptical facettes. Upper Jura ; 

 Wyoming. 



Shastasaurus, Merriam. Includes several large species from the Upper 

 Trias of northern California. Pelvis very robust ; all but first ten ribs single- 

 headed. Cymhospondyhcs, Leidy, from Middle Trias of Nevada, is imperfectly 

 known. 



Order 4. SAUEOPTERYGIA. Owen.^ 



Primitive aquatic reptiles with long neck, lizard-like body, and moderately short 

 tail. Cranium small, with parietal foramen and large supratemporal vacuities. 



^ Andrevjs, 0. W., On Plesiosaurus, Pliosaunis, etc. (Quar. .Joiirn. Geol. Soc. vol. XXXVJI. p. 440), 

 1881.— Also ibid. vol. LIII. (1897), p. 177, and various articles in Geol. Mag. [4], vol. II. (1895), p. 241 ; 

 ibid. vol. III. (1896), p. 145 ; Ann. Mag. Nat. Hist. [6], vol. XV. (1895), p. 333 ; ibid. vol. XVI. 

 (1895), p. 429. — Bassani, F., Sui fossili degli schisti bitumiuosi triassiei di Besano (Atti 1st. Veneto 

 Sei.), 1886. — Beneden, P. ./. van, Deux Plesiosaures du Lias inferieure du Luxembourg (Mem. Acad. 

 Pioy. Belg. vol. XLIII. p. 1), 1880. — Boulenger, G. A., On a Nothosaurian Reptile referable to 

 Lariosaurus (Trans. Zool. Soc. vol. XIV. p. 1), 1896. — Cope, E. IJ., On tbe structure of the skull in 



