6 ME. G. A. BOULENQEE ON A NOTHOSAURIAN EBPTILE 



a small bone to each digit. The digits are five, increasing in length to the third, 

 which equals the fourth, the fifth intermediate in length between the first and second. 

 The first metacarpal is as long as the fifth but more slender ; the second, third, and 

 fourth are equal, half as long as the radius ; the first finger has two phalanges, the 

 second three, the third and fourth have four, the fifth three ; the distal phalanx is 

 obtusely pointed, flattened, and did not support a claw. The phalangeal bones are 

 devoid of condyles. 



The pelvic bones are somewhat crushed and displaced. The left pubis is probably 

 hidden under the ischium, but the right is exposed, and does not show a notch in its 

 posterior border. The ischia form large plates with radiating strise. 



The femur is straight, subcylindrical, but feebly expanded at the extremities ; its 

 length exceeds by one fourth that of the humerus. The tibia is a little longer and 

 considerably broader than the fibula, and not quite half as long as the femur. In the 

 tarsus, a large intermedium and a smaller fibulare are present ; only two very small 

 bones, at the base of the third and fourth metatarsals, are distinguishable in the second 

 row. The metatarsals are more elongate than the metacarpals, and the third and 

 fourth the longest and equal. The phalanges of the pes are stronger than those of the 

 manus, and their formula is different, viz. 2, 3, 4, 5, 4 ; the toes increase gradually in 

 length from the first to the fourth ; the fifth is nearly as long as the third. The pes 

 exceeds the manus by the length of the two distal phalanges of the fourth toe. 



It seems probable, from the structure of the extremities, that this Saurian was better 

 adapted for locomotion in the water than on land, and the digits must have been 

 connected by a broad web. 



On comparing the hand and foot of this Eeptile with those of Mesosaurus, one 

 cannot fail being struck by the concordance in the number of phalanges, and the great 

 similarity in shape of the epipodials and phalangeals. The number of carpal bones is 

 the same in both, but in Mesosaurus the tarsus comprises five elements in the distal 

 row, and the fifth toe, instead of being shorter than the fourth, is a little longer. This 

 agreement, together with other characters, such as the structure of the humerus and 

 the form of the ribs, points to special affinity between the Mesosauria and Nothosauria, 

 as first recognized by Prof. Seeley, This author, in his recent paper on Mesosaurus 

 (25), places Neusticosaurus, a close ally of the Eeptile here described, in a division, 

 Neusticosauria, of the Suborder Mesosauria, characterized by flat articular surfaces of 

 the centrum, coracoid separated from scapula, a notch in the pubis, a long neck and a 

 short tail. As regards the latter character, which, even if founded on a well ascertained 

 fact, would be at most a generic character. Prof. Seeley overlooks his former account 

 of Neusticosaurus, in which he expresses the opinion that the tails of the specimens 

 described by him are imperfect, and also the fine photograph, exhibited in the Geolo- 

 gical Gallery of the British Museum, of a slab from the Lettenkohl of Hoheneck, 

 Wiirtemberg, representing a group of Neusticosaurus ]}usillus, which have the tail 



