222 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



A variety with longitudinal rufous bands is also figured above. 



Jaw : see p. 220. 



Lingual membrane with 129 rows of 24 — 1 — 24 teeth each. .See p. 220. 



The complete anatomy, including genitalia, is figured by Leidy (Vol. I. PI. 

 XV. Figs. 2-4). The penis sac is short, narrow, and cylindrical. The vaa 

 deferens is of a very great length when compared with what it is usually in 

 the other genera. Its lower part, about the length of the penis, is dilated to 

 the size of the latter organ, is strongly muscular, and terminates at the base of 

 the penis sac. The retractor muscle is inserted into the summit of the latter. 

 The lining membrane of the penis sac presents a single, longitudinal fold. At 

 the base of the penis sac is a short, muscular sac, or protuberance, probably a 

 dart sac, although the individual dissected possessed no such instrument. The 

 genital bladder is oval; its duct is as long as the oviduct, and midway receives 

 a long, narrow duct, derived from a granular, glandular organ combined with 

 the testicle in the posterior lobe of the liver. 



(2) Jaw with decided vertical ribs to its anterior surface. 



ARION, F^russac. 



Animal limaciform (see Vol. III. PI. LXIV. Fig. 1). Posterior termination 

 of body obtuse. Integuments crowded with elongated tuberosities on the back, 

 and on the sides with elongated tubercular plates having furrows between. 

 Mantle anterior, oval, small, covered with granulations, free at the front and 

 on the sides, attached posteriorly, containing in its posterior part numerous 

 fine calcareous sandy grains. Locomotive disk not expanded at the margin, 

 when the animal is fully extended very narrow, having in some species a nar- 

 row median band, and in others not. Respiratory orifice at the anterior mar- 

 gin of the mantle, small. Anal orifice contiguous to the former. Orifice of 

 organs of generation under the two last. On the upper part of the posterior 

 extremity of the body is a triangular pore or sinus, with the point directed 

 forwards, a process or projection of the integument serving as a cover to the 

 sinus. 



The genus is not indigenous to North America, the only known species here 

 having been introduced by commerce. 



The genus Avion was separated from Limax by Fe'russac, to contain those 

 species of the latter genus having a terminal pore or sinus. It is universally 

 recognized, and has been fortunate in escaping any confusion of synonymy. 



The habits of the North American species have been given on p. 11. 



I have not been able to give any information regarding two of the species 

 found" within our limits, A. Andersoni (see below, p. 239), and .4. foliolatus. 

 Indeed- there seems so much uncertainty in regard to them, that I doubt their 

 belonging to this genus. For fuller information, see below. This leaves only 

 one species, A. hortensis, Fer., described and figured in Vols. II. and III., and 

 in L & Fr.-W. Sh. N. A , I., referred to A.fuscus, Mull. 



The species was introduced by commerce into Boston many years ago. It 



