44 CALIFORNIA ACADEMY OF SCIENCES. [Proc. .^d Ser. 



thousand feet of what was termed Knoxville strata, but from 

 the uppermost four thousand feet of them. The seventy- 

 seven species enumerated, all of which, with the exception 

 of two or three species of Aucella, are apparently confined 

 to this relatively small stratigraphical range, are almost 

 equal in number to the eighty or more species that are thus 

 far known from the six thousand feet of Horsetown strata, 

 where the individuals are far more abundant. In fact, the 

 actual thickness of strata through which this new and distinct 

 fauna ranges is not yet definitely known, though from the 

 statements made in regard to the locality and position of the 

 different species, we learn that the great majority of them 

 have been found in or near the sections studied in the 

 Sacramento Valley, and that the stratigraphical range is 

 rarely if ever given as greater than three thousand feet 

 below the upper limit of the Aucella range. With the 

 introduction of this new fauna at that horizon the Atccellcs 

 gradually diminish, until at the next immigration of species 

 they entirely disappear. Stanton says of this fauna: ''All 

 but seven of the species are mollusca, including thirty-three 

 species of Pelecypoda, one species of Scaphopoda, eighteen 

 species of Gasteropoda, and eighteen species of Cephalo- 

 poda, of which fifteen are Ammonoids, and three are 

 Belemnites. The other seven species include five Brachio- 

 pods and two Echinoderms." So far as known, the cephalo- 

 pods contain a single species each of Dcsmoceras, Lytoceras, 

 and Phylloccras, forms which are so numerous in the Horse- 

 town, while Hoplites is represented by five species and 

 Perisphmctes by one. 



The two species of Olcostephanus are both new and have 

 not been found in the Horsetown. An important feature of 

 the Gasteropoda is the large number of Turbo species, six 

 species of this shell being described. Two species of 

 Hypstpleu7-a, and three of Cerithium are known. Nothing 

 particularly characteristic is to be noticed with reference to 

 the bivalves, most of which, with the exception of Aucella, 

 have allies among the fauna of the Horsetown. The 

 Brachiopoda, however, deserve mention, the five species 

 being, perhaps, peculiar to this fauna alone. 



