84 Ancella- Bearing Strata of Oregon. 



described forms pass from one to another by such insensible gra- 

 dations as to render it doubtful whether we have in southern Ore- 

 gon more than one true species. 



The Ancellas are generally distributed through the sandstone 

 and limestone in the vicinity of Riddle, Oregon, at an elevation 

 of about 2,500 feet — the lowest exposure known in this section. 

 The rock is extremely hard, with a metallic ring, sometimes al- 

 most wholly composed of fragments of these shells, none of which 

 are found entire. The exposures of these shell-bearing lime- 

 stones are water-worn in appearance, the beds full of pot-holes, 

 grooves and channels, like the bed of some mountain stream at a 

 low stage of water, where the rocks are unequal in hardness and 

 unequnally worn by the running water. 



This exposure is about three miles west of Riddle, about three 

 hundred feet above Cowcreek valley, on the crest of a consider- 

 ble ridge with a deep gorge on either side. If running water 

 caused the erosion noted it must have been at a very ancient 

 date. The sandstone for some distance around contains numer- 

 ous shells, imperfectly preserved. 



Above these exposures are vast bodies and huge clifts of con- 

 glomerate, composed entirely of quartz pebbles. Adjoining and 

 usually above the conglomerate are the nickel mines and the 

 country rock known as olivine, with large masses of serpentine 

 and chromite in many places. Seven miles further west on the 

 top of Big Buck mountain beds of coarse, soft sandstone occur, 

 containing usually only the casts of these shells. 



The Ancella bearing strata of Alaska and British Columbia 

 are considered of the Cretaceous age. Some of the beds in Califor- 

 nia have been referred to the Jurassic . Riddle is about twenty miles 

 south of Roseburg, on the Oregon division of the Southern Pa- 

 cific Railroad. The shells in the exposure nearest Riddle, where 

 they are most abundant, resemble those from near Knoxville, 

 California. The shells from Big Buck mountain are allied to A. 

 erringtoni; some from the east of Riddle appear to be be A. pi- 

 ochii, while others look like A. pallassii. 



Fine impressions of fern leaves occur in a shale of the carbon- 

 iferous (?) age not far beneath the shell-bearing sandstone. 



Aurelius Todd. 



A NEW RHAPHIOMiDAS FROM CALIFORNIA. 



The Dipterous genus Raphiomidas was founded by the Baron 

 Osten Sacken (Western Diptera, page 281), who placed it in the 

 family Midasidae. No mention of this genus is made by Dr. 

 Williston in his excellent ' Synopsis of the Families and Genera 

 of North American Diptera;' in his Table of Families (1. c, 

 pages 9-15) it would fall into the division (26) which contains the 

 Asilidae and Midasidae, agreeing nearest with the characters ac- 

 corded to the latter but differing in that the labella are not dis- 

 tinctly fleshy and the antennae lack the terminal lamella. From 



