125 



portion of a disk. In sninc jrciirni. it is dcpply emarginato, as in LacertUia; 

 l)iit it is usually entire, as in Sauropteri/giu. 



'Vhv liumcriis is a small bone, exceedingly wide in ('liddstes and Platc- 

 carpus, and narrower in Llodoit. It is wider distally than proxinially, lias a 

 Hat shaft, and presents no condyles, l)ut elongate articular surl'aces only. 

 The radius is also a wide l)one, especially dilated at its distal and exterior 

 border. The ulna is nuieh less expanded ; the extremities being subecpial, 

 and tlie shall contracted, l»ut flat. The carpals are small, ilat, and lew in 

 number; they are sui)r()und or hexagonal in outline. The phalanges, meta- 

 carpals, and metatarsals are llattened near the ear|)us, l)ut soon become less 

 expanded and more cylindric at the extremities and at the shaft. The term- 

 inal ones are flat. 



The ]>elvic elements arc slender, and the inferior but loosely-united on 

 the middle line below. The ilium is the longest, and is cpiitc attenuated 

 above, and witliout immediate contact with a vertebra. The pubis is clavate 

 and flat; the v.'ider portion next the ilium, and pierced with tin; tbramen 

 observed in LacertUia. The ischium is broader, and has an angulate poste- 

 rior outline. The femur is equally or more slender than tlie humerus (see 

 the plate oi' Flatecarjms crassartus), and, in Liodon, resembles it in form. It 

 is Hat, without condyles, wider distally, and with a trochanteric tuberosity at 

 the proximal end. The fil)ula is a very wide bone, sometimes constituting 

 three-quarters of a disk. The tibia is, like the ulna, a more slender bone 

 than its companion, with contracted shaft, and subequally-cxpar.ded extrem- 

 ities. 



The phalanges much res('nd)le those of marine turtles, and the pes and 

 manus are of a less rolnist type than in any other order ol' marine p'ptiles. 



jtj/inities. 



The significance of the ordinal characters lias been already pointed out. 

 There remain a iiund)erof peculiarities, not certainly of ordinal value, which 

 are, nevertheless, necessary to consider in estimating the relations of these 

 reptiles to others : 



1. The form and position of tlie coronoid bone are those seen in eryci- 

 !i)rm serpents. 



2. The articulation of the sjjlenial with the angular is only paralleled in 

 the pvllionoid and allied seiiiciits. 



