GENUS TESTACELLA. 



Fig. 1. — Nerve ring of T. 

 haliotidea, Bristol. X 5, showing 

 the arrangement of the gangha. 



Internally, the most important peculiarity, as compared witli the Linm- 

 cidce, is the location of the heart' near the posterior extremity of the body, 

 accompanied by a corresponding change in the position of the pulmonary 

 cavity and anal aperture, the kidney and the shell, which are usually in rela- 

 tion with it. As in Lima.v, the heart is anterior to the kidney, but occupies 

 its right anterior corner, and the auricle is larger 

 than the ventricle, and directed obli(iuely back- 

 wards, the ventricle in front, in consonance with 

 the altered course of the aortic trunks. 



The VISCERAL SAC is almost completely un- 

 twisted, resulting in the pulmonary plexus being 

 moved to the rear of the obliquely-placed heart, 

 Testiicella hemg thus opisthopneumonic; kidney 

 without secondary ureter;^ supra-pedal gland 

 long and sinuous, lyiug free on upper surface of 

 the foot and extending almost to the pi3sterior extremity of the body." 



The Nervous System is chiefly centralized in a nerve ring, encircling the 

 enormous lingual sheath, the closely contiguous cerebral ganglia above it 

 giving off long and thick connectives to the pedal and visceral ganglia whicli 

 are fused together beneath ; the long cerebro-buccal connectives surround 

 the ojsophagus, and the buccal ganglia are fused together or at least in con- 

 tact, not separated by a longlsh commissure as is usual in the Linviculw. 



The olfactory faculty is 

 well developed and exhibited 

 as a large ganglion with ra- 

 mose terminations at the 

 apex of each of the posterior 

 tentacles or rhinopliores.'' 



Simroth also affirms that 

 he has detected a double 

 fringe of nerves of the same 

 sense within the pallial 

 chamber, a relic of the primi- 

 tive osphradium. The eye 

 is small and black and the 

 vision feeble and myopic, the 

 optic nerve, which shows scarcely any dilatation, separating from the nerve 

 of olfaction quite at the base of the tentacles. 



The alimentary canal is simple, showing few flexures ; the mouth very 

 dilatable, its inner surface protected by a thick layer of chitin ; the 

 ODONTOPHORE large, beset with transverse. 



Fig. 2. 



Fig. 3. 



Fig. 2. — Rhinophore of T. haiiotidea{^her IMoquin-Tandon) 

 greatly enlarged, showing the ganglionic enlargement and the 

 ramose terminations of the olfactory nerve, e eye with optic 

 ganglion and nerve. 



Fig. 3. — Pallial olfactory organ or osphradium of T. mangel 

 (after Simroch). o,o. olfactory orifice ; o.c. olfactory ca\'ity ; 

 o.r. olfactory ridge ; r.o. respiratory orifice ; I.e. lung chamber. 



:B^ 



obliquely arcuate rows of slender, barbed 

 and apically-pointed teeth, typical of 

 Beloglossa ;•'' cesophagcs short ; crop volu- 

 minous and muscular, functioning as the 

 digestive sac, and held in position by a 

 sheet of separate slender muscles, arising 

 from the sides of the body, but most 

 conspicuous on the left side ; the true 

 STOMACH is reduced to a small receptacle at first bend of gut near the open- 

 ing of the bile ducts; intestinal tract short, with but two tracts or 

 Dichodromous." 



Fig. 4.— Alimentary canal of T. lialiotidea 

 from Horsham, XlS, showing the simplicity 

 of its course and an unusual development of 

 the vestigial stomach. 



1 .\Ionog. i., p. 293, f. 583. 



4 .Monog. i., p. 226, f. 148. 



2 Monog. i. p. 336, f. 626. _ 

 ilonog. i., p. 267, f. 535. 



3 Monog. i., p. 314, f 604. 

 6 Monog. i.,p. 285, f. 568. 



