APOLLON. 7 
ANTE’RIOR of a bivalve, is the side opposite to that on which 
the ligament is placed; of a spiral univalve, that part of the 
aperture which is at the greatest distance from the apex; of a 
symmetrical conical umvalve, such as Patella, that part where 
the head of the animal lays, indicated by the interruption of the 
muscular impression; of Cirripedes, that part where the ciliz 
protrude; of Brachiopoda, that part which is furthest from the 
umbones. Lamarck and others, have created much confusion 
by their inconsistencies on this subject, describing the same part 
of a shell at one time as anterior, at another, posterior; but 
generally the reverse of the above arrangement, which is 
founded upon the position of the head of the animal, and 
generally adopted. ‘The anterior will be indicated by the letter 
a, in fig. 119, 421, 229, 34, 202. 
ANTIGONA. Schum. Venus Cancellata, Lam. 
AN’TIQUATED. This word, signifying out of date, is used but 
rarely to express that composition which obtains in shells, by 
each fresh deposit or layer of calcareous matter, forming a new 
margin, which being replaced by its successor, no longer con- 
stitutes the margin, and is consequently out of date. 
A’'PEX. This term has no regard to the natural position of a 
shell, but is used mathematically to express the nucleus, or first 
formed part, or point of the spiral cone, of which almost every 
shell may be supposed to consist. From this point the shell 
rapidly or slowly enlarges as it descends and takes a spiral, 
arcuated, straight, oblique, convolute, or irregularcourse. The 
Apex will be indicated by the letter a, in fig. 282, 466. 
A’PERTURE. The entrance to the spiral cavity of univalve 
shells; it is composed of the inner lip, or /adzum, which gene- 
rally forms the axis of the shell, and the outer lip or /abrum on 
the opposite side. In fig. 318, the aperture will be pointed out 
by the letter a. 
APHRODITA. Leach. Cardium Greenlandicum, Auct. fig. 
123*, and other similar species, the teeth of which are very 
indistinct. 
APLEURO’TIS. Rafinesque. Unfigured and imperfectly de- 
scribed, as somewhat differing from Terebratula and Magas. 
A’PLODON. Rafinesque. Genus proposed at the expence of 
Helix, but imperfectly described. 
APLUS'TRA. Schum. Buta Aplustra, Auct. fig. 249. 
APLYSIA’CEA. Bl. The second family of the order Monopleuro- 
branchiata, Bl. The animals composing this family are either 
destitute of shells, or are provided with internal ones. Genera, 
Aplysia and Dolabella. 
APOL'LON. Montf. Ranetua Ranina, Auct. Placed by Blain- 
ville in that division of Ranella, which is characterized as being 
umbilicated, fig. 393. 
