1914] The Ottawa Naturalist. 133 



areas of the skin of the species described by the writer in 1902,* 

 under the name Trachodon marginatus. A figure of the surface 

 markings of a small portion of the skin of this species accom- 

 panied the writer's original description, but the new material 

 brings to light with wonderful distinctness features additional 

 to those already known, and discloses a tubercular pattern of 

 surface ornamentation as unique as it is unexpected. 



Trachodon marginatus was founded on an admirably pre- 

 served maxilla and lower mandibular ramus, with teeth in place 

 having a definite marginal sculpture, and on many bones of one 

 individual with skin impressions. Provisionallyassigned to this 

 species were slender ischia ending distally in a foot-shaped ex- 

 pansion, a pubic bone, a femur, tibiae and other elements of the 

 skeleton. That the association of the footed-ischium with 

 T. marginatus was correct is borne out by the remains of two 

 individuals** collected last summer with which the maxillae and 

 lower jaw are present in one, and the ischia in both. A com- 

 parison .of the new material with that on which the species was 

 based entirely establishes the correctness of the writer's original 

 description. It is with one of these specimens of last summer's 

 collection that the skin impressions are preserved. These im- 

 pressions are from the side in the trunk region, and along the 

 tail. In the former, depressed conical plates or scales, having an 

 oval basal outline, occur at intervals with much smaller, 

 polygonal, tubercle-like, non-imbricating plates filling the inter- 

 spaces. The conical plates strongly resemble limpets in shape, 

 and are about twice their diameter apart. They reach a size 

 of about one and a half inches in length and one and a quarter 

 inches in breadth, with a height of about five-sixteenths of an 

 inch. The comparatively small,' intervening plates resemble 

 the smaller sized plates of Protorosaurus belli, and of Trachodon 

 annectens, Marsh, as described by Osborn.J They range in 

 diameter from about one-eighth up to two-eighths of an inch, 

 an increase in size occurring toward the conical plates round 

 which the largest ones form a ring. A marked feature of the 

 conical scales is a radial crinkling which is most pronounced 

 at the basal circumference and extends about half way up the 

 sloping surface. 



In the tail the same scale pattern is continued but in a less 

 striking manner, its component parts being reduced in size. The 

 conical plates are more nearly circular in basal outline, with a 

 diameter of about half an inch, and a proportionately lower 

 relief. Thev are relatively farther apart than those of the trunk, 



* Op. cit., p. 71, pis. iii-x. **Expediti. n of 1913; found by Mr. Charles H. Sternberg. 

 % Memoirs of Am. r. Mus. Nat. Hist., new series, vol. i, pi. ii; Integument of the I^uano- 

 dont dinosaur Trachodon, p'.s. vi and vii. 



