DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



163 



first true molar is 1.5 inches in length, while the last inferior 

 molar is 2.25 inches long. The pecuharity in the structure of 

 the superior molars consists in the existence of two strong 

 transverse ridges, which connect the inner tubercle with the 

 outer crescents, inclosing a pit between them. These are most 

 marked on the premolars, where also is found the peculiarity 

 of the almost entire fusion of the outer crescents into a single 

 ridge. These united crescents are narrower than in P. major, 

 and the summits of all the crescents are relatively more ele- 

 vated. The number of inner tubercles is the same as in that 

 species; all the teeth have very strong basal cingula, which 

 rise up on the inner tubercle. The last inferior molar is rela- 

 tively narrower than in P. major, and the posterior tubercle is 

 larger and longer and is an elevated cone. 



From the foregoing description it will be seen that 

 Cope based his specific description upon three speci- 

 mens (cotypes) without designating any one of the 

 three as being more typical than the others. (See 

 fig. 95.) The name vallidens, however, from vallum, 

 a wall, seems to refer to the peculiarity in the struc- 

 ture of the superior molars, which 



consists in the existence of two strong transverse ridges, which 

 connect the inner tubercle with the outer crescents. * * * 

 These ridges are most marked on the premolars, where also is 

 found the pecuharity of the almost entire fusion of the outer 

 crescents into a single ridge. 



If we had nothing further to guide us we would thus 

 be led to infer that the upper dentition (Am. Mus. 5097), 

 which best shows these peculiarities alluded to in the 

 name vallidens, should be regarded as the most typical 

 of the three specimens and should be chosen as the 

 lectotype. But in his "Tertiary Vertebrata" Cope 

 (1885.1, p. 700) says: 



The bones containing the maxillary and mandibular teeth 

 were not found together in any instance, so that it is possible 

 that the different series may represent different species. No 

 other species of the genus was, however, found in the locaUties 

 to which the respective parts could be referred. Should these 

 prove not to pertain together, the lower jaws may be regarded 

 as typical of the species. 



As Cope was the "first reviser" of the species there 

 seems to be no escape from the conclusion, if modern 

 rules of nomenclature are to be followed, that the lower 

 jaw (Am. Mus. 5098) must be treated as Cope's 

 lectotype. 



Etymology. — vallum, wall or redoubt; dens, tooth; 

 allusion as explained above. 



Present determination. — This little-known species is 

 allied to but probably specifically distinct from Doli- 

 cJiorTiinus Tiyognathus of Washakie B and Uinta B. 

 It is also more primitive than that species (see below). 



Limnohyus laevidens Cope, 1873 



Cf. Limnohyops laevidens (Cope), this monograph, page 305 



Original reference. — Pal. Bull. No. 11 ("issued Jan. 

 31, 1873"); Am. Philos. Soc. Proc, vol. 13, pp. 35, 

 36, 1873 (Cope, 1873.5). 



Subsequent references. — Cope, On the extinct Verte- 

 brata of the Eocene of Wyoming, observed by the 

 expedition of 1872: U. S. Geol. and Geog. Survey 



Terr. (Hayden) Sixth Ann. Kept., p. 591, 1873 (Cope, 

 1873.6); Tertiary Vertebrata, p. 701, cotype skull, pi. 

 50, figs. 1, 2 (holo type) , fig. 3 (paratype), 1884 [1885] 

 (Cope, 1885.1). 



Type locality and geologic horizon. — Type ("No. 1 "), 

 Cottonwood Creek, Bridger Basin, Wyo.; Palaeosyops 

 paludosus-Orohippus zone (Bridger B). Cotype ("No. 

 2"), Bitter Creek, Washakie Basin, Wyo.; horizon 

 uncertain. 



Cope's cotypes: "A cranium lacking the posterior 

 part of one side and the lower jaw," from Cottonwood 

 Creek ("No. 1," now Cope collection. Am. Mus. 5104). 

 Also "a nearly complete cranium with dentition from 



Figure 96. — Cope's cotypes of Limnohyops laevidens 



After Cope, 1885. One-fourth natural size. A, Am. Mus. 5104, lectotype: Ai, 

 " Cranium lacking posterior part of one side and lower jaw, from Cottonwood 

 Creek" (Cope), "No. 1"; As, upper teeth of the same. B, Am. Mus. 6105, 

 now retered to Palaeosyopst copei, right maxilla, p^m'. 



Bitter Creek" ("No. 2," now Cope collection. Am. 

 Mus. 5105). (See fig. 96.) 



Cope's lectotype: Cope's first-mentioned specimen 

 is the one from Bitter Creek (Washakie B?) (Am. Mus. 

 5105), now referred to Palaeosyops? copei. But the 

 "No. 1" of Cope's description and measurements and 

 the specimen to which the name "laevidens" refers is 

 unquestionably the skull Am. Mus. No. 5104, from 

 Cottonwood Creek (level Bridger B), Bridger Basin, 

 now referable to Limnohyops. Furthermore, in the 

 "Tertiary Vertebrata" (Cope, 1885.1, pp. 701-703, 

 pi. 50, figs. 1, 2) Cope definitely selects, describes, and 

 figures this specimen as the type, again referring to 

 the Washakie specimen as "No. 2" and admitting 

 that its specific association with the other specimen 

 was doubtful. We therefore follow Cope in regarding 



