209 



ICIITIIYOUKCTKS HAMATUS, Cope. 



Represented by a considerable nnmbcr of nnnains of an indivi<liial I'roin 

 the blue Cretaceous sliale, near Russell Spring, on the Smoky Hill River. 



The characters which distinguish this species from /. anaides are numer- 

 ous; hut they are less marked when compared with those of /. ctenodon, partly 

 because the premaxillary bones of the latter have not been preserved. In 

 the first place, the dentary bones of the two arc; of equal length, and su})port 

 the same number of teeth, while the maxillary of L hamatus is shorter, and 

 supports more teeth; it is concave at the proximal part of the tooth-line, but 

 is straight in the corresponding part of /. ctenodon The end of the dentary 

 is furnished with a strong obtuse process or hook directed upward and for- 

 ward, not seen in /. ctowdon. The maxillary behind the premaxillary is in 

 this species thickened, and with two articular surfaces; the proximal looking 

 outward, the distal inward, and separated by an ol)lifpie ridge from the con- 

 dyle. In /. ctenodon, there is but one smootii surface, gradually narrowing 

 with the thinning of the bone from the condyle. 



The premaxillary is less extended antero-superiorly than in the species 

 already described, but supports, as in it, an articular face. There is no groove 

 l)ehind it, as in /. anaides and Portlieus. It disj)lays a surface for osseous 

 articulation to near its extremity on the inner side ; while below it, and on 

 the (external face, near the basis of the first and second teeth, the surface is 

 rugose. Maxillary teeth, forty-three. The dentary supports twenty-five. 

 Tlic anterior hook is obtuse, and rises abruptly to above the apices of the 

 crowns of the teeth. It is knol)be(l above, and supports a lootli not larger 

 than (he others. 



All the cranial bones preserved are not sculptured. 



Portions of the thin Hat ventral spines display the delicalely-grooved 

 striation already observed, while the trenchant edge is Imrderedon one side 

 l)y raised longitudinal stritB. The other side is minutely pitted. 



The vertehrm arc anterior, and without lateral grooves. Thj-ee of them 



arc 0"'.06 in length ; an undistorted one is a little wider llian ('cep, and llie 



cup is 0'°.026 across. 



Mcaaiirements. 



M. 



I^cngtli of tlio ramus mandilmli 0. 174 



Depth at the Bj'in])lijsi3 0.055 



Depth of the pr(Miiaxillary (ohliqiic) 0. U-IU 



Lciif;th of tho preiuaxillary (oUliqnc) 0. OW 



27 c 



