LOCALLY INTRODUCED SPECIES. 459 



with granulations, free at the front and on the sides, attached pos- 

 teriorly, 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 narrow median 

 band and in others not. Respiratory orifice at the anterior margin of 

 the mantle, small. Aual orifice contiguous to the former. Orifice of 

 organs of generation under the two last, bn 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 serv- 

 ing 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 F6russac, 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 con- 

 fusion of synonymy. 



The habits of the i^orth American species have been given on p. 462. 



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

 species found within our limits, A. Andersoni and A. foliolatus (see 

 below). Indeed, there seems so much uncertainty in regard to them 

 that I doubt their belonging to this genus. For fuller information see 

 above. This leaves only one species, A. Jiortensis, F6r., described and 

 figured in Vols. II and III, and in L. & Fr.-W. Sh. N. A., I, referred 

 to A.fuscus, Miill. 



The species was introduced by commerce into Boston many years 

 ago. It still exists there,* specimens having been found by me in 1871, 

 from one of which I extracted the jaw and lingual membrane here de- 

 scribed. I have compared the figures of the genitalia of A. hortensis 

 given by Lehmann and A. Schmidt t with those given by Leidy in Terr. 

 Moll. U. S. There is a difierence in the position of the retractor muscle 

 of the penis. Leidy places it at the base of the penis sac, Lehmann at 

 the top, Schmidt omitting it entirely. The last two authors figure a 

 retractor to the duct of the genital bladder, and so does Leidy (though 

 in the description of the plates he refers it to the vagina). Lehmann 

 figures a retractor also to the genital bladder itself. Lehmann's figure 

 of the genitalia of A.fuscus (Plate VI, Fig. 2) agrees more closely with 



» Specimens can readily be found in gardens between Chestnut and Mount Vemoa 

 streets above Willow street, as well as elsewhere. 



tDer Geschlecbtsapparat der Stylommatopboren, 1855. 



