388 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



No type is expressly given by Mojsisovics for this sub- 

 genus, but the first species mentioned is Trachyceras 

 chiesense Mojsisovics ^ which is merely a fragment, and 

 could hardly have been the typical form. The first form 

 described is Trachyceras riidolphi Mojsisovics, which is 

 much more characteristic, though not nearly so common 

 nor so well known as many other species cited as belong- 

 ing to this group. If the author had chosen one particular 

 species as the type, it would probably have been Trachy- 

 ceras archelaiis Laube, which has all the characters cited in 

 the diagnosis, is well known in all its details, and is so 

 common as to be chosen as a zone fossil. 



Protrachyceras is characterized by its short body-chamber, 

 compressed, but robust, whorls, moderately involute form, 

 open umbilicus, and central abdominal furrow. The ribs 

 are provided with spines arranged in spiral rows, and the 

 ventral furrow is bounded by only a single row of tubercles 

 on each side. This is the character that distinguishes it 

 from Trachyceras s. str., which possesses a double row of 

 knots on each side. Most species of Protrachyceras are 

 more evolute than those of Trachyceras s. str., but this 

 character is not constant, and in the opinion of the writer 

 the separation of the two groups is purely artificial, without 

 either stratigraphic or phylogenic value. 



Subgenus Anolcites Mojsisovics. 



1893. Anolcites, Mojsisovics, Cephalopoden der Hallstatter Kalke, Bd. II, 

 p. 621. 



In naming this subgenus Mojsisovics did not select any 

 species as the type, but the first one mentioned under the 

 description is Trachyceras doleritictimyio]s,\soV\cs'^. Anol- 

 cites differs from Trachyceras s. str. in being more evolute, 

 with wider umbilicus, and lower whorls. The ventral fur- 

 row is scarcely developed, and the ribs cross the venter, 

 although a row of tubercles is developed on each side of 



iSeeBibliog. 21 — p. 95, pi. xxxiv, fig. 4. 



*See Bibliog. 21— p. 103, pi. xiii, fig. 5; pi. xxxvii, fig. i. 



