order iv SAUROPTERYGIA 175 



siiturally united with a pair of stout scapulae, which develop oblique dorsal processes. 

 The coracoids are not much extended in the median line, and their antero-internal 

 margin is notched and incomplete; apparently the space between them and the 

 clavicular arch was tilled during life by cartilage. The humerus is moderately long, 

 curved, and very robust ; it is pierced distally by an entepicondvlar foramen. Radius, 

 ulna, and metacarpals are likewise rather long and slender, the paddle-shaped form of 

 limb being not yet fully acquired. 



The bones of the pelvic arch are robust, and owing to their loose articulation, 

 usually occur detached in the fossil state. The ilium is very short and stout, some- 

 what expanded distally, and provided with two articular facettes. Pubis and ischium 

 are both of large size, narrowed and thickened at the acetabulum, and distally ex- 

 panded ; a small obturator foramen jjersists in the pelvis. The femur is longer and 

 more slender than the humerus, nearly rectilinear, moderately thickened at the 

 extremities, and with rounded articular faces. The remaining bones of the hind limb 

 are imperfectly known. 



Nothosaurus is an exclusively Triassic genus, and occurs most abundantly in tin 

 Muschelkalk of Southern Germany. N. mirabilis, Minister, is the typical and best- 

 known species, attaining a length of fully 3 m. Smaller species are known from the 

 Bimtsandstein and Lettenkohle. The so-called Parthanosaurus, Skuplios, from the 

 Raibl Beds of Yorarlberg, is doubtfully distinct. 



Conchiosaurus, v. Meyer. Muschelkalk; Esperstadt, Brunswick. 



Simosaurus, v. Meyer. Skull broad and depressed, with obtuse snout. 

 Teeth short, obtusely conical or clavate, the crown strongly striated. Muschel- 

 kalk and Lettenkohle. 



Pistosaurus, v. Meyer. Known only by the skull, which tapers anteriorly, 

 and attains a length of 35 cm. Premaxillae elongate and slender, the small 

 narial openings placed between them and the maxillae. Nasals greatly 

 reduced and displaced posteriorly. Palate with an unpaired vacuity between 

 the premaxillae. Muschelkalk ; Franconia and Silesia. This genus is made 

 by Baur the type of an independent family. 



Family 2. Plesiosauridae. 



Limbs paddle-shaped,, hours of second segment much shortened, and the five digits 

 elongated by supernumerary phalanges. Clavicular arch tending to diminish in sizi 

 as the scapulae increase, the latter sometimes becoming fused with each other and the 

 coracoids in the median line. Coracoids much extend, d along median symphysis, 

 and uniting with either the scapular or clavicular arch anteriorly. Sclerotic plates 

 present. Trias to Cretaceous. 



Plesiosaurus, Conyb. (Figs. 278-280). Head small, neck very long, tail of 

 moderate length. Snout not elongated, orbits elliptical and placed near the 

 middle of the skull, supratemporal vacuities large, irregular. External nares 

 small and close to the orbits. Postero- lateral angles prominent. Inter- 

 pterygoidal and posterior palatine vacuities small. Mandibular symphysis 

 short. Teeth acutely conical, longitudinally grooved; anterior ones some- 

 what enlarged. Coracoids meeting in a long symphysis, scapulae separated 

 by a well-developed clavicular arch. 



The number of cervical vertebrae varies among the dill'erent species between thirty 

 and forty. The centra are but slightly biconcave, and united to the neural arches 

 by suture ; the marks of their attachment form with the neural canal a cruciform 



