58 AMERICAN MESOZOIC MAMMALIA 



Except for this abnormal, post-mortem extrusion, it agrees in every detail with Pi of 

 Dryolestes. Marsh's referred specimen (1887, PI. IX, fig. 6) shows the true canine, 

 but is broken oflE just back of P2 and hence did not draw his attention to his error. 

 Marsh explicitly pointed out that the "molars agree in general form with those of 

 Dryolestes." His figure was drawn from the specimen as it lay half buried in matrix, 

 with the cusps partly hidden, and hence might be imagined to contradict his correct 

 interpretation of the molars in his text. Following the figure rather than the text, 

 Osborn stated ( i888a, p. 238) that "The molars resemble those of Dryolestes, but lack 

 the third postero-internal cusp." This has ever since been accepted as true and has been 

 supposed by Osborn, Winge, Gregory, and others to show that Astheiwdon forms a 

 link between the heelless symmetrodonts and the typical dryolestids. Cleared of the 

 matrix, the molars substantiate Marsh's view that they were of dryolestid type, and 

 Dryolestes and Asthenodon prove to be synonymous. 



Only one species of Dryolestes can now be recognized. In 1879 (p- 215) Marsh 

 named a supposed second species Dryolestes vorax, distinguished as being smaller, 

 with the horizontal ramus more slender, less curved, and less compressed. The holo- 

 type. Y.P.M. No. 1 1818, has but one tooth which proves on restudy to be a first molar 

 of docodont type (the docodontids had not then been discovered save for this imperfect 

 example). Dryolestes vorax is a nomen nudufu, the type not being specifically identifi- 

 able. In 1887 ( PI. I X, fig. 3) Marsh figured a good lower jaw as Dryolestes vorax, but 

 this specimen is not conspecific, or even congeneric, with the holotype. It is probably 

 referable to Laolestes eminens — the teeth are strongly worn and slight differences 

 from the type of the latter species are probably due entirely to this cause." 



Marsh also created a species Dryolestes gracilis. The species is valid, but must be 

 referred to Amblotherium. In the latter genus it becomes a homonym. It is treated 

 below under the name Amblotherium debilis. 



Dryolestes priscus M.zrsh. 1878 



1878. Dryolestes friscus, Marsh, Amer. Jour. Set. (3) XV, 459. 

 1880. Stylacodon validus. Marsh, Amer. Jour. Set. (3) XX, 236. 

 1887. Asthenodon segnis, Marsh, Amer. Jour. Set, (3) XXXIII, 336. 



Type. — Y.P.M. No. 11820. Fragment of right lower jaw with one molar. 



'° It has been generally assumed that the specimens figured in Marsh 1887 as representative of 

 the various species are the types of those species. In some instances this is incorrect, as reference to the 

 original descriptions would have indicated. It has been possible to identify the type specimens of the 

 various species beyond any question, the original descriptions. Marsh's notations with the specimens, and 

 a manuscript list of types in his hand furnishing a triple check. Merrill's Catalogue of Types . . . in 

 the Department of Geology, United States National Museum lists as types (i.e., holotypes) several Meso- 

 zoic mammal figured specimens which are referred, not original types. Pt. II, p. 21, No. 2138 is not the 

 type of Allacodon pumilus. P. 24, No. 2862, paratype, or referred specimen, not cotype of Asthenodon 

 segnis (Marsh designated a type and specifically said that this specimen was referred). P. 35, No. 2727, 

 not type of Dryolestes vorax, as just pointed out above. P. 61, No. 2693, not type of Stylacodon gracilis 

 but a later specimen, treated by Marsh in the same way as No. 2727. 



