PRIMITIVE REPTILES 661 



ceratobraiichials, and four pairs of ossified epibranchials. Atlas 

 short, cylindrical, concave behind, its body composed of a single 

 bone, that is not divided into odontoid and intercentrum, sup- 

 porting the paired neural arch; closely united to skull without 

 intervening cartilage. Vertebrae notochordal, the neural arches 

 each composed of paired bones meeting in the middle line above, 

 but not united, and without spines; with a prominent diapophy- 

 sis on each side of the arch for the support of the (for the most 

 part single-headed) ribs; no intercentra and no free chevrons. 

 Limb bones small, without ossified articular ends, the meso- 

 podials evidently unossified, and the girdles not yet recognized. 

 No dermal ossifications. 



If the foregoing characters be correct, and I feel quite sure 

 they are, it will necessarilj^ follow that, if Lysorophus be a real 

 reptile, it must occupy a place all by itself as a separate subclass, 

 without known descendants or antecedents. It is an established 

 principle in paleontology that an organ or bone once lost never 

 reappears in any descendants. We know of no reptile in which 

 the lacrimal, postfrontal, postorbital, jugal and quadratojugal 

 are all wanting; we know of but one order, the Sauropterygia, 

 in which single-headed ribs have become purely neuracentral 

 in attachment, and surely no one will include Lysorophus in that 

 order! Nor could it be genetically allied to the Lacertilia, because 

 the Squamata have single-headed ribs attached to the centrum 

 only, a more primitive reptilian condition to which the single 

 headed neuracentral ribs of Lysorophus could not have returned. 

 And all Lacertiha have bones in the skull which are wanting in 

 Lysorophus; in none does the prefrontal articulate with the 

 parietal, excluding the postfrontal. That Lysorophus is widely 

 remote from all other contemporary reptiles may be seen from 

 the foregoing pages. The entire loss of the intercentra, not 

 only from the cervical, dorsal and caudal vertebrae, but also 

 from the atlas, is a character unknown in any Amniote verte- 

 brate, but is the universal condition among amphibians. And 

 so also, is the presence of four (not three) pairs of epibranchials. 

 If, therefore Lysorophus be really a reptile, it had become so 

 extremely divergent from all other known reptiles by the close 



JOURNAL OF MORPHOLOGY, VOL. 23, NO. 4 



