Geology. 41 1 



3. The systematic relationships of certain American Arthro- 

 clires ; by L. Hussakof, Bull. Amer. Mus. Nat. Hist., vol. 

 xxvi, pp. 263-272, with pi. xlv, and 8 text figures. — In this 

 brief paper Dr. Hussakof describes two new genera, each with 

 but a single species, and expresses doubt as to the validity of the 

 genus Protitanichthys of Eastman, the species of which he refers 

 to the well-known Coccosteus. r. s. l. 



4. A revision of the Mitelodontidce ; by O. A. Peterson. 

 Memoirs of the Carnegie Museum, vol. iv, No. 3, 1909, pp. 

 41-146, with pis. liv-lxii and 80 text figures. — An admirable piece 

 of work in which Mr. Peterson has brought together all that has 

 been published of these swine-like creatures, enriching it with 

 many observations of his own upon the material at Yale, the 

 American Museum, the Carnegie Museum, and elsewhere. 



The introduction is followed by a revision of genera and 

 species, followed in turn by a history of the discovery and 

 excavations in the famous Agate Spring fossil quarries in western 

 Nebraska ; the paper closing with a full anatomical description 

 of the most notable specimen that these quarries have produced, 

 the huge Dinohyus, a creature of rhinocerine bulk. 



The relationships of the various genera, their distribution in 

 space and time and an account of the probable feeding habits 

 close the memoir. The bibliography includes 114 titles, so 

 extensive is the literature upon this interesting group, r. s. l. 



5. A nev) species of Procamelus from the Upper Miocene of 

 Montana, with notes upon Procamelus madisonins Douglass • 

 by Earl Douglass, Ann. Carnegie Museum, Vol. 5, Nos. 2 and 

 3, pp. 159-165, with pis. ix-xi and two text figures. — Mr. 

 Douglass describes briefly the skull, jaws, and cervical vertebra?, 

 constituting the type of the new species of camel, Procamelus 

 elrodi, found by him in the Lower Madison valley in Montana. 

 The animal possessed a large skull with a relatively large brain- 

 case when compared with other species of its genus. The type 

 skull of Procamelus madisonins, described by Douglass in a 

 previous paper, is figured for the first time and the description 

 amplified. R. s. l. 



6. Notes on the fossil mammalian genus Ptilodus with 

 descriptions of new species; by James W. Gidley, Proc. U. S. 

 Nat. Museum, Vol. xxxvi, pp. 611-626, with pi. 70 and 9 text 

 figures. — In this important paper Mr. Gidley gives some of the 

 results of a special expedition to the Fort Union beds of Sweet 

 Grass county, Montana. One specimen in particular, the type of 

 Ptilodus gracilis n. sp., is remarkably complete and adds greatly 

 to our knowledge of the Allotheria or Multituberculata. Mr. 

 Gidley's conclusions may briefly be summed up as follows : 



The genus as newly defined combines the upper dentition of 

 the supposed genus Chirox with the lower dentition of Ptilodus, 

 thus proving the synonymy of the genera. The same is probably 

 true of the genera Bolodon and Plagiolax. 



