MESOZOIC CHANGES IN FAUNAL GEOGRAPHY. 375 
But near by, in southeastern Idaho, are found Lower Triassic* 
fossils, of which the most characteristic are Weekoceras gracihtats, 
White, 17. mushbachianum, White, and Xenodiscus aplanatus, White. 
Very closely related forms have been described from the Salt 
Range of India by Waagen,’ and from northern Siberia by Mojsis- 
ovics,3 and from the Himalayas by Griesbach.* It is clear then 
that the post-Paleeozoic revolution had not cut off the West Coast 
region from direct connection with the Indian and Arctic provinces. 
But these two provinces were probably cut off from the Medi- 
terranean province, since it has been shown by Mojsisovics® that 
during Lower Triassic time Z7volitine were common, Dinaritine 
rare, but MWeekocerata almost unknown in the Mediterranean 
region; while in the Arctic province there were no 77rolitine, but 
many Dinaritine and Meekocerata. Also Waagen® has recently 
shown that the same thing is true of the Salt Range and Hima- 
layan Lower Triassic faunas. 
The Idaho beds were, therefore, deposited on the extreme east- 
ern border of a sea that stretched from the Salt Range eastward 
to America, and northwards to Siberia. And for the Lower 
Trias alone the Arctic-Pacific Trias province of Mojsisovics will 
hold good. In this province somewhere we have to seek for the 
ancestors of the Ceratitide, which Mojsisovics? says will be found 
among some of the Meekocerata, while Karpinsky * thinks it prob- 
able that the Meekocerata descended from the goniatite stock 
Prolecanitide. 
Middle Trias —Rocks of the Muschelkalk series are only 
doubtfully known in California, but a comparatively rich fauna 
of this age has been described from the Star Peak range in 
*C. A. WHITE: Twelfth An. Rep. U. S. Geol. Surv. Terr., Part I., pp. 105-118. 
2 Pal. Indica, Salt Range Fossils, I. Productus Limestone Fossils, Cephalopoda. 
3Mém. Acad. Impér. Sci. St. Pétersbourg, Series VII., Tome XXXVI., No. 5. 
Arktische Triasfaunen. 
4 Records Geol. Surv. India, Volume XIII. Part I., 1880. 
5 Arktische Triasfaunen, p. 149. 
6Jahrb. K. K. Geol. Reichsanstalt Wien, Vol. XLII., 1892, pp. 384-5. 
7Abhandl. K.K. Reichsanstalt Wien, Vol. VI., Part II., Cephal. Hallst. Kalke 
le sPante pei: 
® Ammoneen der Artinsk-Stufe, p. 43. 
