HANDLES : ANATOMY OF TTTRRITELLA COMMUNIS. 57 



material has also been obtained through the kindness of Mr. E. W. L. 

 Holt, the naturalist in charge of that station. Mr. "Woodward kindly 

 placed the material at my disposal, and I am further indebted to him 

 for much valuable assistance. 



External Characters. — It will be unnecessary for me to do more 

 than call attention to one or two poiuts of interest in connection 

 with the external characters of the animal, as they have already 

 been fully described by other observers [2]. On the right side of 

 the animal, in the cephalic region, two conspicuous folds or lobes 

 [Fischer, 3] are present (PI. Yl, Fig. 1); the smaller of these is 

 situated low down, and from its innervation I should consider it to be 

 the remains of an epipodium (ep.). The larger fold lies immediately 

 underneath the right tentacle, and is seen to be the continuation of 

 ■ a, fleshy ridge bounding a well-marked groove, the nature of which 

 I shall refer to later on. This fold may be termed the genital flap (g.f. ). 

 jjThe snout is short and broad ; on it are situated awl-shaped diverging 

 . tentacles; the eyes, slightly prominent, lie at the outer bases of the 

 tentacles. The margin of the mantle is fringed, as in Cerithium, and 

 is moreover furnished with numerous papillae (PI. VI, Fig. 2, m.p.), 

 the longer ones having their edges fimbriated. The foot is very short, 

 .truncate in front, attenuated and obtuse behind, grooved beneath; the 

 opereuligerous lobe is simple. Three pedal glands are present. In 

 the anterior region of the foot there is a slight transverse cleft lined 

 by glandular cells, which pour their secretion into the cleft. In 

 jthe posterior region there is a small median gland (sole gland), which 

 i opens by a short duct near the end of the sole. In addition to these 

 .median glands, there is an unpaired structure on the right side of 

 ,the foot, situated just above the operculum; this may be termed 

 .the s up r ((opercular gland. These structures are of minute size, and 

 .were only to be made out by the examination of a series of longi- 

 tudinal and transverse sections through the head and foot. The 

 .operculum is a horny, circular, multispiral plate, with a central 

 , nucleus and fimbriated edge ; it closely resembles the operculum of 

 Potamides. 



, Internal Anatomy. — The Alimentary Canal. — The mouth is 

 - situated near the tip of the snout on its ventral surface ; its lateral 

 walls are furnished with a pair of horny jaws, composed of minute 

 ! chitinous tessera?. The buccal mass is fairly large ; its muscular 

 ] system and radula-cartilage are well developed. A moderately-sized 

 j radula-sac is present. 



. A pair of very small salivary glands are situated at the sides 



of the buccal mass near its junction with the oesophagus ; they 



immediately overlie the buccal ganglia. The salivary ducts open 



l into the posterior portion of the mouth. The total length of glands 



. and ducts is only about two-thirds that of the buccal mass. A very 



long, narrow oesophagus (PI. VI, Fig. 2, ces.) leads out of the buccal 



mass, and, running parallel with the columella muscle, underneath 



the genital groove (g.g.), reaches the stomach (st.), which it enters 



. on the right side a little above the median constriction. The stomach 



is a fairly large structure, divided by a median constriction into two 



