73 1 SCIENTIFIC RECORD FOR 1883. 



at Washington, with quite satisfactory results. His conclusions have 

 been embodied in an article published in the Proceedings of the TJ. S. 

 National Museum (vol. V, pp. 449-4S.°>), entitled "Remarks on the Sys- 

 tematic Arrangement of the American Turdidse." 



The most essential characters of the group are given as the booted 

 tarsi, coincident with the spotted plumage of the young. The most 

 prominent featurfe of the new arrangement, contrasted with that most 

 current in the United States, is that the Mimince have been removed 

 altogether from the family, the genus Cichlherminia, formerly regarded 

 as a connecting link between the two subfamilies, being broken up into 

 Cichlherminia proper, and Margarops, the former belonging to the true 

 Turdince, the latter to the Mimince, which are referred to the neigh- 

 borhood of the TroglodytinoB. Furthermore, the Saxicolidce (including 

 JSialia), and the Lusciniidce have also been included among the Turdidce, 

 while the Myadestince have been given rank as a subfamily under the 

 same head after having been removed from the PtilogonaUdce, among 

 which, however, Myadestes leucotis is left under the new generic term 

 Entomodcstes. The groups have been made more natural by removing 

 heterogeneous elements and putting them in their proper place. Thus 

 Turdus pinicola was made the type' of the new genus Ridgwayia and 

 placed among the Sialece, while Turdus fiavipes and allies were trans- 

 ferred to the Myadestine genus Platycichla, which the author shows to 

 have been fouuded upon a female of the species in question or a very 

 nearly related one. 



Mammals. 



Extinct Rodents of America. — The extinct rodents, whose remains have 

 been resurrected from the Tertiary deposits of the United States, have 

 been examined by Professor Cope, and interesting details have been 

 supplied. No evidence has been furnished as yet of the existence of 

 any representative in the lowest beds (Puerco-Eocene epoch), but spe- 

 cies have been found in the next succeeding (Wasatch-Eocene epoch), 

 and have continued to the present in gradually increasing numbers. 

 Representatives of apparently nine families have been found in pre-pli- 

 ocene strata, of which three are extinct and the rest still existing. The 

 older extinct families were related to the squirrel-like types, and are (L) 

 Ischyromyidas, with thirteen species, twelve of the Eocene and one of 

 the Oligocene, representing three genera ; (2) Mylagaulidw, known only 

 through one species found in the Upper Miocene ; and (3) a form named 

 Heliscomys, either of an undifferentiated or doubtful family, described 

 from the jaws of a species found in the Oligocene. No remains of any 

 of the existing families have been found earlier than the Oligocene ; 

 during that epoch the beavers, squirrels, mice, and hares were repre- 

 sented by extinct genera, and in the Miocene the porcupines and gophers 

 ((jeomyidae) left remains. " The ancient genera all differ from their 

 modern representatives in the same way; that is, in the greater con- 

 striction of the skull just posterior to the orbits and accompanying ab- 



