AGEIOLIiMAX AGllESTLS. 



lOo 



.) 



Fig. U7.— Internal 

 shell of Agyioliinax 

 agrcstU, X 1. 



(Markland Grip, 

 Derbyshire, Mr. C.T, 

 IMusson). 



r in sliaiip, spotteil with brown 



Description. — Animal liniaciform, with large but flattened tubercle.s; of a some- 

 what uniforiJi whitish or pale oclireons ground colour, but sometimes dull lavender 

 or other tint, often mottled, speckled or reticulated with brown or black, and at 

 times totally suffused witli black ; BODV somewhat compressed and keeled towards 

 the tail; TKNTACLH.s dark coloured ; shield more than one-third the total length 

 of the animal, rounded in front and behind, concentric stride not deep, with the 

 nucleus on the right side and towards tlie rear ; KL.SWR.VTOKY OKIFICL with a 

 broad usually unpigmented raised ring, whicli is cut anteriorly by the anal cleft; 

 SOLE pale and longitudinally tripartite, the side areas sometimes darker, especially 

 towards the tail ; S()LE-friN(;e separated as usual from the body by a furrow, 

 containing a row of elongate tubercles, upon which the body tubercles rest uncon- 

 foruiably. Mucus plentiful and viscous, often clear when crawling, but becoming 

 milky-white on irritation, due to innumerable particles of carbouate of lime. 



Length usually about 35 mill. 



Shell white, oblong-oval in shape, somewhat 

 convex above and correspondingly concave below, 

 usually rather thin ; NUCLEU.S distinct and placed 

 towards the left side of the posterior margin of 

 the shell ; concentric lines of growth perceptiljle, 

 margin membranaceous. 



Length, 4 mill. ; width, 2J mill. 



Internally, the cerebral ganglia are triangul 

 especially at the margins, the commissure grey or 

 darkly spotted ; the stomato-gastric or buccal 

 ganglia with longish commissure and dark-brown 

 connectives ; the parieto-splanchiiic ganglia are 

 fused with the pedal ganglia, ami both display 

 short commissures ; the vestigial osphradium can 

 be traced as a ridge and channel across to tlie left 

 of the respiratory chamber ; the oigan of Semper 

 shows well-developed inferior lobes. 



The ALIMENTARY CANAL is trlodronious, com- 

 posed of the stomach tract and three intestinal 

 coils; the INOE.STIVK TRACT is the shortest, tlie 

 CESoi'HAGa.sis also short, and the voluminous CROR 

 of a light-brown colour, thin, and scarcely fur- 

 roweil, having the long and much-indented SALI- 

 VARY GLANDS adherent to its sides. The last tract 

 or rectum has, about mhl-way, a short crecvim on 

 the right side generally directed backwards, and 

 laid upon the upper surface of the crop. The DIGES- 

 TIVE GL.iND is of an ochreous colour, the ri"ht 

 lobe e.xtending quite to the caudal end of the body, 

 and in common with the wliole intestinal mass 

 has been subjected to a noticeable spiral twist in 

 such a way as to indicate that an external .shell if 

 present would be a dextrally-coiled one. 



The CEPHALIC retractor origin- 

 ates in the median-line, behind the 

 lung, from three or more roots, which 

 immediately unite to form a simple 

 slender band, and divides usually lint 

 not invariably about half-way. There 

 is considerable variation in the details 

 of the furcation ; irsually the BUCCAL 

 and tentacular branches separate 

 at nearly the same point, but some- 

 times the slender buccal branch is an 

 offshoot of one or other of the ten- 

 tacular retractors, or may arise from 

 the main-muscle before the tenta- 

 cular forking. The buccal retractor 

 is always deejdy divided in English 

 forms, but not usually down to its 

 origin or root, as Dr. Sinnoth states is the case in the German siiecimens 



23/11/03 



/ 



Fii;. 118.- 



Nerve centres 



of A. a^fL-ifis, 



showing otocysts 



X 8. 



iChristchiirch, 

 in Hants S., Mr. 

 C. .Ashford). 



Fig. 119.— 

 Alimentary canal of 

 A. agnslis, X 2, 

 with the sali\-ary 

 glands removed and 

 showing the rectal 

 cecum. 



(Chrislchurch, in 

 Hants S., Mr. C. 

 Ashford). 



Cephalic retractors of^. ag7\ 

 the \ariations to which they are 



Fig. 120, represent 

 usual arrangement. 



lis, X 2 

 able, 

 usual form. Fig. 121 

 Fig. 122, the unusual. 



