1S70.] •^''^ [Cope. 



mitcliillii it is a dift'erent plane, like a rabbet. It may be added, that the 

 glenoid cavity is nan'ower and deeper. 



Four teetli from Barnesboro, indicate marked characters. They are 

 much compressed as in L. mitcliillii, and the posterior cutting edge is 

 well developed and forms a narrowed extremity of an elliptic section. 

 The anterior ridge less developed. In three crowns there is no trace of 

 the unequal division by these edges, as in Mosasaurus sp. One probably 

 from the premaxilla is more abruptly recurved than the others, with base 

 rather expanded inward?. The distinguishing character of these teeth, 

 which separates it from L. mitcliillii, is the abundant longitudinal fluting, 

 and striation of the enamel. The grooves are deeper and shallower, 

 coarser at the base; the strife are fine, continuous and rugose. These are 

 not seen in L. mitcliillii. The general form of the crown is short, broad 

 at the base and well curved posteriorly and inwards. 



Lines. 



Elevation of crown and pedestal 21 



" alone 16 



Antero-posterior diameter do. at base 12 



The lateral element of the atlas is represented from the inner side 

 in Fig. No. 3. The anterior termination of the inferior ala, and the 

 articular face for the centrum, are as in M. mitcliillii. The inner articu- 

 lar face is divided by a vertical depression ; the posterior, or that meeting 

 the odontoid process, is quite prominent and distinct. The anterior 

 facet for the occipital condyle, is transversely divided by a depression. 



The form of the cervical vertebrae is so much like that of the Mosasau- 

 rus dekayi, as to be readily taken for those of a small example of that spe- 

 cies. The first dorsals, or those without hypajiophysis, are more elongate 

 than in the latter, and the body is more contracted, so that the ball pre- 

 sents a projecting rim all round. This is readily knocked off in the rough 

 handling the specimens usually receive. The cup is also proportionately 

 expanded. Posterior dorsals where the diapophyses issue half from the 

 centrum, have the latter slightly deiiressed; where the diapophysis comes 

 three-fourths from the body, the articular faces are a broad transverse 

 ovate, well expanded on the margins, below which the surface is slightly 

 striate. In the longer or anterior dorsals, the rudiment of zygosphen and 

 zygantrum is well marked. 



Unfortunately, no caudal vertebrae of this species have been preserved, 

 — so that I do not know their form. The posterior dorsals are so much 

 more depressed than in Liodon laevis that future discovery may justify 

 the generic separation of the genus Neetoportheus which I originally ap- 

 plied to this animal. 



For the largest measurements I refer to Dr. Leidy's Essay on Creta- 

 ceous Reptiles, where the description of the large specimens of Macrosau- 

 rus laevis belong to the present species, and have served in part as my 

 types. 



