146 
JfAUTILOIDEA. 
£ndoceras avus, Eichwald, sp. 
1845. Ortlioceratites duplex, ^Murcli., Vern., and de Keyserl. Geol. de 
la Itussie d’Europe, vol. ii. pt. 3, Paloeont. p. 351 (pars), pi. xxv. 
i.2,a,h. 
1860. Cochlioceras avus, Eichwald, Lethaea Rossica, vol. i. Seconde 
Section de I’ancienne Periode, p. 1251, pi. xlviii. f. 4, a, b, 
Sp. Char. Shell straight. Section circular. Rate of increase, 
roughly calculated, about 1 in 10 , but the specimens are too frag- 
mentary for accurate measurements to be taken. Septa rather ap- 
proximate ; in a small specimen 14 lines in length, with a diameter 
of 9^ lines at the larger, and lines at the smaller extremity, they 
are about 2 lines distant. In a larger specimen they are distant 
5 lines where the diameter is 1^ inch. The diameter of the siphuncle 
very slightly exceeds 5 of that of the shell. A small fragment of the 
test adheres to one of the specimens, but whether this be the outer 
or the inner layer I am unable to state. It is perfectly smooth. 
Bemarl's. Upon this species Eichwald founded the genus Coch- 
lioceras, which, however, has not been recognized by palaeontologists. 
He describes it as having a marginal siphuncle, with numerous 
constrictions (“ etranglemeuts ”), by which the latter appears as if 
articulated. This appearance is caused by the narrowing of the 
septal necks, as may be seen in Orthoceras simjilicissimum, G. & F. 
Sandb., to which Eichwald also refers. There is nothing whatever 
remarkable in such a feature ; it is met with in many of the Ortho- 
ceratidae. 
Horizon. Orthoceras-lAmQsicmQ ( = Areuig-Llanvirn). 
Locality. St. Petersburg. 
Fairly well represented in the Collection. 
Endoceras trochlearej Hisiuger, sp. 
1831. Orthoceratites trocMearis, Hisinger, Antecku. i Physik och 
Geognosie, Haft. 5, p. 12, tab. iv. f. 3. 
1837. Orthoceratites trochleoj-is, Hisinirer, Lethaea Svecica, p. 28, tab. ix. 
f. 7. 
? 1837. Orthoceratites vaginatus, Broun, Lethaea Geogn. Zweite Aufl. 
Band i. p. 100, Taf. i. ff. 9, a, b (not f. 9, c). 
1841. Orthoceratites vaginatus, von Buck in Karsten’s Archiv fiir 
INlineralogie, &c. Band xv. Heft i. p. 37, tab. ii. f. 11. 
? 1849. Melia trochlearis, d’Orbigny, Prodr. de Paleontologie, vol. i. 
p. 4. 
? 1851. Oj'thoceras vaginatum, Salter, Quart. Journ. Geol. Soc. vol. vii. 
p. 177, pi. X. f. 7. 
