224 
NAtrriLorDEA. 
Gomphoceras tumescens, Barrande. 
1867. Gomphoceras tumescens, Barrande', Syst. Sil. de la Boheme, vol. ii. 
pt. i. p. 316, pi. Ixxxi. ff. 18-30. 
Sp. Char. Shell having a distinct and uniform curvature on the 
ventral side, hut almost straight on the dorsal. Circular in trans- 
verse section. The rate of increase in the septal part of the shell 
is about 1 in 2. The body-chamber occupies about ^ of the total 
length, and it is about equal in capacity to the septate portion of 
the shell. The aperture is T-shaped, and, taken as a whole, is 
strongly inclined towards the ventral side, forming an angle of about 
30° with the vertical axis of the shell. The larger orifice is con- 
siderably dilated in the middle and is lobed at either extremity ; a 
moderately short channel leads into the smaller orifice, which is oval 
in shape and does not project beyond the ventral margin. The 
septa are separated from each other by a space equal to about i the 
diameter of the shell ; their convexity equals about | of the same. 
The siphuncle varies in position according to the age of the indi- 
vidual. In the young it is midway between the centre and the 
ventral border ; in older individuals it is only the width of its own 
diameter removed from the centre ; its elements are probably cylin- 
drical, but they are not completely known. 
The test is ornamented with fine, subregular, transverse striae 
which form a sinus upon the ventral side. Very close-set longitu- 
dinal striae are visible on some specimens with the aid of a lens, 
and there are on the body-chamber a series of faint longitudinal 
impressions, which, however, are not always present. This species 
is distinguished from its nearest allies by the globular form of its 
body-chamber, as well as by the position of the siphuncle and the 
longitudinal markings on the test. The species nearest to it is G. 
amphora., which, however, has a smooth test and much less developed 
body- chamber. 
Horizon. Etage E (=Salopian). 
Locality. Xarlstein, Bohemia. 
Eepresented in the Collection by two examples. 
Gomphoceras scrinium ?, Hall. 
1864. Gomphoceras scrinium, Hall, 18th Beg. Rep. on the New York 
State Cabinet of Nat. Hist. p. 350, pi. xviii. tf. 1-3. 
1866. Gomphoceras Marcyce, Winchell and Marcy, Mem. Boston Soc. 
Nat. Hist. vol. i. pt. i. p. 101, pi. hi. f. 8. 
1879. Gomphoceras so'inium, Hall, Pal. of New York, vol. v. pt.ii.p.318. 
1882. Gomphoceras scrinium, "Whitfield, Geol. of Wisconsin, pt. hi. 
Palseont. p. 360. 
