G. Tt. Wieland — Upper Cretaceous Turtles. 187 



nally the columns of the prefrontals converge below nearly to 

 an acute angle and are directed forward, also much backward 

 in Lytoloma (Yale specimen No. 913a), thus forming a strong 

 internal base on the vomer. They restrict the nasal meatus, 

 leaving its diameter less than that of the columns. 



The internal nares in the present specimen open far back ; 

 but the long, broad, and massive vomer is fairly complete, and 

 it is not likely that the palatines closed in behind it to further 

 roof the narial passage. If so, herein may lie a marked differ- 

 ence from the still more specialized Eocene Lytolomas from the 

 London Clay and the Landenien inferieur of Belgium. In 

 describing the skull of Lytoloma crassicostatum Owen, Lydek- 

 ker says : " one of the first points which strikes the observer 

 [on comparison with Thalassochelys] is its extreme shortness, 

 the width at the widest part of the temporal arch being exactly 

 equal to the length from the occipital condyle to the muzzle ; 

 whereas in the Loggerhead the former diameter is considerably 

 less than the latter, whilst in Chelone the difference between 

 the two diameters is still greater. Still more noticeable is the 

 backward position of the posterior nares, which are situated at 

 a point one third the distance from the condyle to the muzzle, 

 as indeed is mentioned in M. Dollo's description of the Belgian 

 specimens. In that description it is, however, stated that the 

 boundary of the posterior nares is formed by the development 

 of the palatal plates from the pterygoids. So far, however, as 

 can be seen from the present specimen, it would appear that 

 this border is really constituted by the palatines, since on 

 either side there seems to be a distinct suture separating the 

 bones forming the border of the posterior nares from the 

 undoubted pterygoids. Looking at the arrangement of the 

 palatines in the Loggerhead, it would seem much more natural 

 that these should be prolonged backwards, rather than that the 

 pterygoids should assume the condition assigned to them hy 

 M. Dollo. In either case the vomer is excluded from the 

 posterior nares, but its position anteriorly is not shown in this 

 specimen." (It is obscured by the lower jaw which is in 

 place.)" 



The Carapace and Plastron. 



The specimen (Yale Catalogue, No. 625) on wfeich the fol- 

 lowing description is mainly based was received from the West 

 Jersey Marl Company, May 1, 1869. It is from the old, long 

 unworked marl pit, one and one-half miles east of the village 

 of Barnsboro, Gloucester county, New Jersey. Willows, 

 holly, pine, etc., now grow scatteringly over this area of former 

 excavation some thirty acres in extent, which has yielded so 

 many other interesting fossils, among them the remarkably 

 tine carapace and plastron Osteopygis Gibbi. 



* Lydekker, loc. cit. 



