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



curving to the broad venter without any marked abdominal shoulders. 

 Umbilical shoulders abruptly rounded, with the inner walls steep. Umbilicus 

 deep and narrow, but exposing the umbilical shoulders of the inner whorls, and 

 becoming wider with age. Body-chamber long, apparently comprising at 

 least an entire revolution. 



Surface ornamented with numerous closely set radial ribs, that run nearly 

 straight from the umbilicus across the venter, usually dividing on the flanks. 

 On the ribs are spiral rows of short spines or knots, varying from nine to 

 thirteen rows on each side, showing on!y on the outer shell and not on the 

 cast. This sculpture is the same over all parts of the whorl, and there is no 

 interruption on the venter nor any ventral furrow. This character easily dis- 

 tinguishes Trachysagenites from Trachyceras, with which it is associated, 

 and with which it has often been confused. The spiral arrangement of the 

 spines separates it from Halorites. 



The septa are ammonitic, more deeply digitate than is usual in the Tropi- 

 toidea. The external lobe is divided by a shallow siphonal saddle into two 

 short branches. The first lateral lobe is long, rather broad, and divided at 

 the end into two branches. The second lateral is shorter and narrower, but 

 also digitate. On the umbilical shoulder is a distinctly individualized aux- 

 iliary lobe, not unlike the second lateral, but smaller. The antisiphonal lobe 

 is long and narrow, flanked by two similar lobes on each side. 



This species grew to a considerable size, specimens of 

 nearly two hundred millimeters diameter having been found, 

 and the relative measurements remain remarkably constant 

 from adolescence to maturity, except that in adolescence the 

 whorl is slightly broader in proportion to the height, the 

 involution somewhat less, and the umbilicus slightly broader. 



The young shells are subglobose and nearly smooth, 

 resembling the Glyphioceratidas of the Carboniferous. The 

 lateral ribs appear at the diameter of four millimeters, and 

 the spiral rows of knots at five millimeters. The septa pass 

 from the goniatite to the ammonite stage at a little under 

 three millimeters. 



Sagenites herbichi Mojsisovics is very like -5'. erinaceus 

 Dittmar, as figured by Mojsisovics in " Cepholopoden der 

 Hallstatter Kalke", II, plate c, figures 2-4, but differs from 

 that species in its greater lateral compression, more numer- 

 ous spiral rows of knots, and much more numerous and finer 

 radial ribs ; also in S. herbichi the lobes are shorter and 

 broader, the second lateral is small and scarcely divided, 

 and the auxiliary is represented only by a small notch on the 

 umbilical shoulders. 



