BALANUS. 79 



Conchology, did not consider his genus as established, not having 

 seen the hinge. 



AXIS. The imaginary line, round which the whorls of a spiral 

 shell revolve. The extremities of the axis are pointed out in fig. 

 379, by the letters, a. a. See "Columella." 



AZECA. Leach. Fam. Colimacea, Lam. —Deser. " Animal like Bu- 

 linus, with subcylindrical, rather obtuse shell, covered with a 

 polished periostraca (epidermis) ; aperture pear-shaped, curved 

 and pointed at the top ; the margin thick, obtuse, united all 

 round and toothed ; the axis imperforated." Gray's edition of 

 Turton's British Shells, page 189.— Obs. The Turbo Tridens of 

 Montagu, upon which this genus is founded, resembles Bulinus 

 lubricus in general form and character. Both these shells differ 

 from the true Bulini in having the peritreme entire, and in being 

 pellucid and glossy. Azeca differs from Bulinus lubricus in 

 having three teeth in the aperture, two on the inner lip and one 

 on the outer. Not seeing the necessity for creating a genus on 

 grounds so slight, I have simply transcribed the description given 

 above, leaving others to form their own conclusions as to the pro- 

 priety of separating this shell from the genus Bulinus. Britain, 

 Central and Southern Europe. Azeca Tridens, fig. 290. 



AZEMUS. Ranzani. Conia, Leach. 



BACULITES. Lam. Fam. Orthocerata, Bl. Ammonacea, Lam. — 

 JDescr. Straight, conical, tubular, laterally compressed ; chambers 

 divided by very sinuous lobed septa, the last elongated ; aperture 

 elliptical; siphon dorsal. — Obs. This genus differs from Ortho- 

 ceras in the same manner in which Ammonites differs from Nau- 

 tilus, having its septa sinuated and branched. A Baculite might 

 be described as a straight Ammonite. This genus is known only in 

 a fossil state. It is found in the Cretaceous Limestone of Maa- 

 stricht and Valognes. Fig. 484. B. Faujasii. 



BALANUS. Brug. (an Acorn ; " gland de Mer." Fr.) Order 

 Sessile Cirripedes, Lam. Fam. Balanidea, BL— Descr. Shell com- 

 posed of six valves articulated to each other side by side in a circle, 

 by the insertion of lamina ; closed at the base by a flat, cylin- 

 drical or cup-shaped valve, by which it is generally attached ; and 



