352 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



of Allosaurus ferox had an aperture in the maxillary in front of the 

 antorbital opening. The context appears to indicate that "Allosaurus 

 ferox " is a slip of the pen for Allosaurus fragilis, just as Labrosaurus 

 ft vox seems to be called Labrosaurus fragilis on page 270. At any 

 rate, this is the only mention that Marsh made of the skull of either 

 L. ferox or ^4. fragilis. In the definition of the family Labro- 

 saurida? a he mentioned no part of the skull but the lower jaw. 



On page 270 of the work last cited Marsh referred a third species 

 to Labrosaurus, namely, L. sulcatus. This is done in the explanation 

 of Plate XIII, fig. 1; and, so far as the writer is aware. Marsh 

 nowhere else mentioned this species. Three views of a single tooth 

 are given, but there is no description and no statement as to the origin 

 of the specimen. 



Inasmuch as no teeth or parts of the skull were, so far as Marsh in- 

 forms us. present with the type of L. lucaris, and only teeth or parts 

 of the lower jaw appear to have been represented in the types of the 

 other species, one is at a loss to understand on what grounds the 

 second and third species were referred to Labrosaurus. Further- 

 more, it may be worth while to inquire whether L. ferox and L. 

 sulcatus are congeneric. 



The type of Z. sulcatus is a tooth which, judging from Marsh's 

 figures, presents a crown 30 mm. high, with a base whose antero-pos- 

 terior diameter is 12.5 mm. and whose transverse diameter is 12 mm. 

 There is a posterior face which appears to have been somewhat con- 

 cave, its outer boundary being formed by a crenulated, its inner by a 

 smooth, carina. The outer face of the tooth is ornamented at the 

 base by about eight ridges, of which only three remain at the apex. 

 The inner and the posterior faces are represented as being smooth. 



As already stated, the jaw of L. ferox presented to Marsh little or 

 nothing of the teeth. The crowns of all the functional teeth are miss- 

 ing and the roots were almost wholly concealed by matrix. A section 

 of the base of the crown furthest in front showed above the envelop- 

 ing sandstone. Of this matrix the writer has remoA r ed enough to 

 expose a part of the outer and front faces of the tooth. The inner 

 face had been almost wholly absorbed by the successional tooth, of 

 whose apex about mm. are now laid bare. The functional tooth 

 had an antero-posterior diameter of 15 mm. and a transverse diameter 

 i >f !» mm. The latter diameter was near the front of the tooth, a fact 

 which indicates that the anterior cutting edge had subsided far above 

 the base of the crown. The hinder edge seems to have reached the 

 base. The outer and anterior faces and the little that remains of the 

 inner face are wholly smooth. The inner face. too. of the succes- 

 sional tooth is perfectly smooth and both the anterior and posterior 

 cutting edges are crenulated. 



"Aiuer. Jour. Sci., L. 1S!ir>, p. VX\ ; Dinosaurs of North America, p. 239. 



