bloomer: on the anatomy op tagelus, 221 



parts of the retractor pedis posterior muscle, a position anterior to the 

 posterior adductor muscle. The branchial nerve takes a deep bend 

 anteriorly before reaching the gills. 



The pedal ganglia are situated between the transverse pedal muscles 

 close to the caecum of the crystalline style, but some little distance 

 anterior to the distal end of it. 



Tageltjs divistjs (Spongier). 



The animal measures from the anterior side of the anterior adductor 

 muscle to the posterior side of the posterior adductor muscle 25 mm., 

 and is 11 mm. deep. Dorsally it is curved outwardly, but along the 

 ventral surface is nearly straight. The mantle-lobes (Fig. 4, M.L.) 

 are connected with the anterior side of the anterior adductor muscle, 

 whence they first outline a large anterior curve, and afterwards pass 

 posteriorly in nearly a direct course, until a position almost ventral 

 to the posterior adductor muscle is reached before the marginal parts 

 are joined together, thus denoting the great extent of the pedal 

 aperture. The foot (Fig. 4, F.) is comparatively larger, deeper, and 

 more muscular. In the single specimen under examination it lies in 

 an antero-ventral direction, but whether this is its natural resting 

 position is doubtful, as there is some indication of more than normal 

 tension of the muscles in and near the anterior region of the proximal 

 portion of the foot ; however, the fact that the range of the pedal 

 aperture extends so far posteriorly in the different species of Tagelus 

 and the presence and situation of certain pedal muscles point to the 

 use of the foot in a ventral as well as an anterior plane of movement. 



The proximal portion of the siphon (Fig. 4, Ex.S. and In.S.) is 

 situated between the mantle-lobes, a little antero-venti-ally to the 

 posterior adductor muscle, whilst laterally it is united with the inside 

 surface of each mantle-lobe, thus quite enclosing the posterior portion 

 of the pallial cavity with the exception of the siphonal apertures. 

 Behind this coalesced line the mantle-lobes (Fig. 4, P.L.P.) extend 

 separately some distance posteriorly, so enabling them, when necessary, 

 to completely envelop the free siphonal tubes (Fig. 4, JEx.S'. and 

 In.S'.). The latter are separate from each other with the distal ends 

 pointing dorsally, and, though somewhat contracted, they are relatively 

 shorter than those of allied species. Anteriorly the proximal portion 

 of the siphon continues on each side of the animal as a siphonal 

 retractor muscle (Fig. 4, S.R.M.), which is short, thick, and rounded, 

 but soon spreads out into an ovate-shaped body, and from the external 

 surface adheres to the adjacent valve of the shell. 



When contrasted with the other species of Tagelus it will be 

 seen that T. divisus possesses quite distinctive characters. Its 

 resemblance to Soleciirtus Bomheyi is noticeable in the muscular 

 mantle-lobes, the strongly developed muscular foot, the diminished 

 length of the free siphonal tubes, and the power of the posterior parts 

 of the mantle-lobes to completely envelop them, when necessary ; but 

 it differs from this and the other species in its greater depth, in the 

 comparative largeness of the anterior and posterior muscles and of the 

 musculus cruciformis, in the length of the retractor pedis posterior 



