the Buccal Paris of the Molhisca, 77 



foliaceous expansions, grooved (sulcated) inside, and destined to 

 conduct the particles of food to the mouth, and they may thus 

 be considered passive prehensile organs. 



In the Calyptrseidse the same organ is composed of a single 

 pair, which is represented in all drawings of these mollusks as 

 two intertentacular tubercles. In reality these tubercles are 

 flat inside, grooved as in the Acephala, and probably used as a 

 pair of forceps, as appears from their relative position in different 

 specimens. In Cupulas the palpi form a long haustellum-like 

 tube, with a narrow slit on the upper side. In Dentalium and 

 Siphonodentalium they form a closed, flat tube. 



In the Doridce the palpi are situated near the outer oral aper- 

 ture, and are sometimes of a linear form, with a longitudinal 

 groove on the middle, sometimes foliaceous (Hexabranckus) or 

 meeting together in a semicircle (Lamellidoris) , or they become 

 the oral veil. 



In Conus, Terebra, and perhaps Pleurutoma this veil is de- 

 veloped into a large infundibuliform sucking-cup, which dis- 

 appears when the haustellum is protruded. This veil was for a 

 long time regarded as the proboscis, until Dr. Gray* showed 

 its real nature. In Conus tulipa and C. striatus the edge is 

 divided into many digitations. (Voyage de PAstvolabe ; Mrs. 

 Gray's figures, i. t. 10. f. 6, and 12. f. 2.) 



In the gymnosome Pteropoda the oral veil is divided into 

 several conical " arms," provided with numerous suckers, and 

 probably corresponding to the grooves in the labial palpi of 

 Acephala and Calyptrreidse. 



In the Cephalopoda these "arms" are still more developed, 

 and united by a membrane, which sometimes extends to the tips 

 (Cirroteuthis, Eschricht). 



Under the name "velum," as employed by Loven, very dif- 

 ferent organs are confounded. I believe three kinds may be 

 distinguished : — 



1. The oral veil, formed by the palpi or lips, an organ 

 for prehension or locomotion (Cephalopoda, larva of Opistho- 

 branchia, e. g. Doris), or even partly available as a male organ 

 (hectocotyl of the Cephalopoda), as in the Spiders. The "mem- 

 brane orale" of D'Orbigny, found in the decapod Cephalopoda, 

 seems to me a kind of suspensorium, like the " brids " of the 

 funnel. 



2. The tentacular veil, situated further from the mouth. It is 

 placed, in Pleurobranchus, above the mouth, and formed by the 

 union of the anterior tentacula (vibracula in Aplysia). In 



* " On the Head of the genus Conus," Ann. Nat. Hist. Aug. 1853, p. 176. 



