134 gibbons: on w. Indian pulmonifera. 



Chondropoma plicatulum, Pfr. Puerto Cabello. The animal 

 suspends itself by a very thin but strong silk-like filament, 

 I- to |-in. long, issuing from betv^een the operculum and the 

 outer lip, two-thirds of the latter's length from the suture. This 

 mode of suspension (which is similar in Tiidora megaclieila, 

 P. & M.) is wholly different from that of the South African 

 Cydostomas ; the latter attach their shells to branches by 

 means of a pellicle of dried mucus, very brittle and proceed- 

 ing from the edge of the columellar lip.* 



During almost every month of the year I have collected 

 specimens of various species of Chond?vpoma, and have 

 invariably found that shells with fully formed apertures bear 

 but a small proportion to those having it immature. This 

 is not the case with Tudora and Choanopoma, in which genera 

 it is rare to find a specimen with an imperfect mouth. 



Helicina lirata, Duel. Puerto Cabello and Vera Cruz. 



H. substriata, Gray. Barbadoes. Lives on trees. A very pretty 

 species and variable, specimens being frequently chrome- 

 yellow, bluish, or dark red. 



H. subfusca, Mke. St. Thomas. A variety in form occurs, 

 broader and more flattened. In color some are dark rich 

 reddish, others pale transparent greenish. 



January ji, iSyS. 



* Since writing the above, Mr. Tye's exhaustive paper on MoIIuscan 

 Threads has appeared in this journal (i., p. 401). Mr, Tye makes a slight 

 error in giving Cirithidea decollata, L., as an instance of a mollusc suspending 

 itself by threads. Woodward's figure at p. 209, Man. Mollusca, is C. ohtttsa. 

 Lam. I have seen C. decoiluta at iNatal covering the trunks of marsh trees to 

 sucli an extent that not an inch was unoccupied, but they were attached by a 

 trifle of brittle mucus passing (rom the lip to the tree in the same manner as 

 in brackish-water Litiorins, and doubtless produced in the mode described 

 by Mr. Tye as being adopted by Helices. 



The suspensory thread of C. pUcaiiduin is clearly a very different affair. 

 Its shape, length and flexibility, combined with the fact that it issues Irom be- 

 tween the lip and the operculum, indicate a totally distinct method of 

 manufacture. 



J.C. ii. May, 1879 



