On the Skvleton of a large Plesiosaur. 407 



AiiV. — Note on the Skeleton of a lurge Plcsiosaur (lUionia- 

 Irosauriis tlionitoui, sp. n.) front the Upper Lias of 

 Northamptonshire. ]iy Charles W. Andrews, D.Sc, 

 F.ll.S. (liritisli .Museum, Natural History). 



(I'lililislied by permission of the Trustoob of the IJritisL Museuui.) 



[Plates VII.-IX.] 



SoMK years ago tl>e skeletou of a very large Plesiosaur was 

 (li>('(n(MX'd iu the Upper Ijiassic be;ls of Kiiigstliorpe, 

 Nortliamptousliire, and, although unfortunately some 

 })ortioiis were lost before the value of the fiud was re- 

 cognised, the remaining bones were collected by H. Gerard 

 'llioriiton, Esq., of Kiiigsthorpe Hall, who has presented 

 them to the British Museum. The portions of the skeleton 

 preserved are : the anterior part of the skull and the 

 greater part of the mandible, about 14 cervical, 3 thoracic, 

 21—25 dorsal, 4—5 sacral, and 17 caudal vertebrte (many of 

 these are still united with one another), numerous portions 

 of the ribs, and, most important of all, the nearly complete 

 limb-girdles with the humeri and femoi'a — the distal |)or- 

 tious of the paddles are wanting. All the bones preserved 

 are in very good condition, and are remarkable for their 

 massive solidity. 



'I'he Skull. — Unfortunately, only the anterior portion of 

 the skull is preserved : on the right side the lateral portions 

 as far back as a point some distance behind the orbit ar(i 

 preserved, the maxilla, transpalatine, and anterior portion of 

 the jugal being present ; on the left side this portion is 

 wanting, the maxilla being broken off obliquely sonie 

 distance in front of the external nasal opening. 



In a general way the skull seems to have resembled that 

 of lihoma/eosaurus cramptoni, Carte and Jiaily^, sp., an 

 almost complete skeleton of which was obtained from the 

 Kettleness Alum Works (Up[)er Lias), near W'liitby, and is 

 now preserved in the ^luseum of tScienee and Art, Dublin. 

 A cast of this specimen is exhibited in the Fossil Reptile 

 (jallery of the British Museum. Certain differences 

 between the skull of this specimen and that now described 

 will be noted below. 



The snout is broad and depressed, and the pren)axillary 

 region is strongly marked otf by a broad notch, dee[)est 

 at the point where the maxillo-premaxillary sutures cross 



* Journ. Roy. Dubliu Society, vol. iv. p. 1(30 (ISHO). 



2b* 



