ORDER IV SAUROPTERYGIA 175 



siiturally united Avitli a pair of stout scapulae, wliicli develop oblique dorsal processes. 

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

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

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

 curved, and very robust ; it is pierced distally by an entepicondylar 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 tlieir 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 persists in the pelvis. The femur is longer and 

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

 extremities, and with rounded articular faces. The remaining bones of the bind liml) 

 are imperfectly known. 



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

 Muschelkalk of Southern Germany. N. miraUlis, Münster, is the typical and best- 

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

 Buntsandstein and Lettenkohle. The so-called Parthanosaurus, Skuphos, from the 

 Raibl Beds of Vorarlberg, is doubtfully distinct. 



Coiichiosaurus, v. Meyer. Muschelkalk; Esperstädt, Brunswick. 



Swiosaurus, 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, w^hich tapers anteriorly, 

 and attaihs 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. 



Limhs paddle-shaped, bones of second segment much shortened, and the five digits 

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

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

 coracoids in the median line. Coracoids much extended along median Symphysis, 

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

 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, irregulär. 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 iiumber of cervical vertebrae varies among the ditferent 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 



