720 



SCIENCE. 



[N. S. Vol. I. No. 26. 



as a crust, up into which the magma 

 advanced, not only by displacement, btit 

 absorption. For we have no trace appar- 

 ently of the original basement upon which 

 the Calaveras formation was deposited. In 

 these relations of batholite to disturbed and 

 metamorphic crustal rocks we have a strik- 

 ing analogy with the relations which obtain 

 between the Laurentian granites and the 

 metamorphic rocks of the Ontarian system 

 in the Lake Superior region. The amphi- 

 bolites and other schists of ' auriferous 

 slates ' are petrographically the same as 

 many of the schists of the Ontarian system. 



The invasion of the Jurassic and earlier 

 rocks by the Sierra Nevada batholite seems 

 to have been accompanied, or perhaps pre- 

 ceded, by uplift and the development of 

 mountain structure. During early Cre- 

 taceous time these mountains were pro- 

 foundly eroded, for on the edge of the valley 

 of California we find the Chico Cretaceous, 

 the earUest of the ' Superjacent ' series, re- 

 posing upon the worn surface of the grauo- 

 diorite. The Chico is followed by the lone 

 and later Tertiary formations. In part con- 

 temporaneously with the lone, but chiefly 

 at a later period, there were spread over 

 portions of the region important sheets of 

 gravel. Associated with these are flows 

 of rhyolite and andesite. The rhyolite 

 flows serve as a means of separating the 

 ' older ' from the ' later ' gravels. The an- 

 desitic flows were contemporaneous chiefly 

 vsdth the first of the later gravels. These 

 gravels constitute the once famous placers 

 of California. Since they were spread over 

 the Sierra slope, the latter has been tilted so 

 as to accentuate the grade and intensify the 

 downward corrasion of the streams. As a 

 consequence of this corrasion, we now find 

 only remnants of the gravels and volcanic 

 flows reposing on the tops of nearly flat 

 ridges between the river gorges. 



Andrew C. Lawson. 



University of Califobnia. 



On the \_Harvest Mice\ Species of the Gemtg 

 Reithrodontomys. By J. A. Allen. 8° 

 May 21, 1895. From Bull. American 

 Museum of Natural History, New York 

 (pp. 107-143). 



Dr. Allen has just published a much 

 needed revision of the Harvest Mice — a 

 group of small mammals differing from other 

 murine rodents in having the upper incisors 

 deeply grooved. Since Dr. Allen's studj- is 

 based on upwards of 900 s]3ecimens (two- 

 thirds of which belong to the rich collection 

 of the U. S. Department of Agriculture) it 

 is probable that future researches will add 

 little to the results here published, so far 

 as the United States forms are concerned. 

 The name of the common species of the 

 Carolinas is changed from humilis to lecontei. 

 Fifteen species and subspecies are recog- 

 nized, 12 of which inhabit the southern and 

 western parts of the United States. Seven 

 of the United States forms are accorded full 

 specific rank. One of these, R. montanus of 

 Baird, is known from the type specimen 

 only, which was collected in Colorado more 

 than 40 years ago and is in very poor condi- 

 tion. When additional specimens are ob- 

 tained from the type locality it will probably 

 displace one of the other species. Another, 

 R. arizonensis from the Chiricahua Moun- 

 tains, is separated from R. longicauda of 

 California, chiefly on geographic grounds. 

 In the case of one of the subspecies ad- 

 mitted — R. longieaudus paUidus — it is not 

 likely that Dr. Allen will be followed by 

 other mammalogists. Respecting this form 

 he says : "I find myself greatly embarrassed 

 as to which of three courses to pursue in 

 the matter, namely : ( 1 ) To refer R. palUdus 

 to R. longicmida as a pure synonym of the 

 latter; (2) to treat jR. ^jaKifZiw as one of sev- 

 eral local phases of R. longicauda; (3) to 

 let the name stand in a subspecific sense 

 for a generally dispersed paler southern 

 form of R. longicauda, as opposed to true 

 longicauda of the regiou from about Monterey 



