December 9, 1921] 



SCIENCE 



567 



ing the Recent fauna, and overlies the deposit 

 in which Pleistocene vertebrates are found. 

 In excavating the older bed dense accumula- 

 tions of mammalian remains were encount- 

 ered. This deposit is in general comparable 

 to these occurring at Eancho La Brea. The 

 exhumed material was, however, not so well 

 preserved as that from the asphalt bed near 

 Los Angeles. This seems due, in a measure, 

 to a prevailing earthy matrix showing some- 

 what less impregnation by petroleum than in 

 the Eancho La Brea beds. 



A small collection of bird remains from 

 the McKittrick deposit was submitted to Dr. 

 L. H. Miller for examination. A prelimi- 

 nary statement has been kindly given by Dr. 

 Miller as follows: 



1. Of the ten species thus far determined, six are 

 aquatic or semi-aquatic in habit. With more care- 

 ful examination to determine exact identity of 

 ducks and waders, this proportion will be increased. 

 Quite the reverse is true of the Eancho La Brea 

 beds. 



2. The golden eagle {Aquila clirysaetos) is the 

 most abundant species of land bird. One hawk 

 (Circiis), one caracara, {Folyhorus), and two fal- 

 cons {Falco sparverius and F. near fuscocerules- 

 cens) are the only other raptors. No owls or vul- 

 tures appear in the collection. 



3. Farapavo is not represented. A single quail 

 bone represents the great group of Gallinae. 



4. Shore birds (Limicolse), so rare in the Eancho 

 La Brea beds, are very abundant here. More speci- 

 mens of this group are present in the collection 

 of 100 specimens from McKittrick than in all the 

 50,000 examined from Eancho La Brea. 



5. So far as examined there appear no extinct or 

 extra-limit al species not found at Eancho La Brea. 

 On the other hand Teratornis, Farapavo, the great 

 list of condors, vultures, eagles, old world vultures, 

 and owls are thus far lacking. 



6. The caracara, the indeterminate falcon, and 

 the two storks, Ciconia and Jaiiru, give the same 

 suggestion of semitropic climate as in the case of 

 Eancho La Brea. 



Following is a provisional list of the Pleis- 

 tocene mammalian fauna known from the 

 McKittrick locality: 



^nocyon dirus (Leidy) 

 Canis, near ochropus Esch. 



Felis atrox Leidy 



Felis, near daggetti Merriam 



Arctotherium, near sinrnm Cope 



Mylodon, sp. 



Equus occidentalis Leidy 



Antilocapraf, sp. 



Bison, sp. 



Camel, slender limbed form 



Mastodon, sp. 



Several of the mammalian species listed 

 above are known from Eancho La Brea. The 

 dire wolf (JEnocyon dirus), the great lion 

 (Felis atrox) and the horse {Equus occident- 

 alis) also occur in the asphalt beds near Los 

 Angeles. Machaerodont cats have not been 

 recognized at the McKittrick locality. The 

 bear (.Arctotheriuvi) and the ground sloth 

 (Mylodon) occur in both deposits, although 

 the forms represented at McKittrick may be 

 specifically separable from the types found 

 at Eancho La Brea. A camel with slender 

 limbs is certainly distinct from the largo 

 Camelops hesternus found at Eancho La Brea. 

 Further collecting at the McKittrick local- 

 ity will bring out the relationship between 

 this assemblage and the Eancho La Brea 

 fauna. The contrasting features that are 

 recognized at present may result from a geo- 

 graphic separation of the two asphalt de- 

 posits. It is probable that the environmental 

 conditions prevailing in the southern portion, 

 of the Great Valley of California during the 

 Pleistocene were somewhat unlike those ex- 

 isting in the vicinity of Eancho La Brea, 

 On the other hand, it may be that the faunal 

 differences are to be interpreted as indicating 

 separate stages of the Pleistocene. 



John C. Merriam, 

 Chester Stock 



SPECIAL OIL-IlVrMERSION OBJECTIVES 

 FOR DARK-FIELD MICROSCOPY 



Dark-field microscopy was introduced by 

 Joseph Jackson Lister in 1830, and by the Eev. 

 J. B. Eeade in 1837. The optical principles 

 were clearly enunciated by F. H. Wen- 

 ham in 1850-1856, and apparatus substant- 

 ially as now employed was made and de- 

 scribed by him for use with high powers. 



