Geology . ence only, and alwaysrepresented by different species. On the other hand, in the Pacificprovince, Aucella (Fig. 387, k, I, m), which is wTholly absent fromthe Gulf region, is extremely abundant in the Knoxville beds,and Belemnites, Rhynchonella (Fig. 387, r), Crioceras, (Fig. 387, c), Phylloceras (Fig. 387, 6), and Lytoceras (Fig. 387, a), are common, while rare or absent from the Gulf province. Stanton, Jour. Geol., Vol. V, 1897, p. 607. THE COMANCHE AX PERIOD. 135 Trigonia (Fig. 386, /) is common in both, but the species are notrelated. It will be noticed that
Geology . ence only, and alwaysrepresented by different species. On the other hand, in the Pacificprovince, Aucella (Fig. 387, k, I, m), which is wTholly absent fromthe Gulf region, is extremely abundant in the Knoxville beds,and Belemnites, Rhynchonella (Fig. 387, r), Crioceras, (Fig. 387, c), Phylloceras (Fig. 387, 6), and Lytoceras (Fig. 387, a), are common, while rare or absent from the Gulf province. Stanton, Jour. Geol., Vol. V, 1897, p. 607. THE COMANCHE AX PERIOD. 135 Trigonia (Fig. 386, /) is common in both, but the species are notrelated. It will be noticed that the pelecypods (Fig. 386, d-h),gastropods (Fig. 386, i-l), and echinoids dominate in the Mexico-Texan region, the oyster family being foremost, while the cepha-lopods (Fig. 387, a-c), and Aucella (Fig. 387, k, 1, m), a pelecy-pod, dominate the Pacific fauna, though the list of gastropods(Fig. 387, d-h) and pelecypods (Fig. 387, i-q) is considerable therealso. Corals and crinoids are rare in both provinces. e — f Fig. 386.—The Comanchean fauna of the Texan province. Echixoids: a, Holastersimplex Shum.; b, Diplopodia texanum Roemer; c, Hemiaster dalli Clark. Pele-cypoda: d, Anatina austinensis Vaughan; e, Homomya austiiiensis Vaughan;/, Trigonia emoryi Conrad; g, Lima lOaeoensis Roemer; h, Pecten texanus : i, Fusus texanus Vaughan; /, Turritella budaensis Vaughan; k,Ceri-ihium (?) texanum Vaughan; I, Trochus Sp. Coral: m, Parasmilia texana Vaughan.(After Vaughan.) The question of the cause of this distinctness has already beenalluded to, but cannot be positively answered. The complete dis-tinctness and the contrast of aspect are obviously most completelyexplained by a land barrier separating the two provinces, much as atpresent, and there is now no proof that this was not the case. If, how-ever, the oceans joined, the best appeal perhaps is to ocean currentsof different temperatures. Assuming from general meteorologicalprinciples the existence of trade-winds
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