portions arising during chemical metamorphosis of 

 the cells into that substance. The laminae are 

 here, as in Nature everywhere, the indications of 

 formation and of transformation or change. The 

 epiphragm maybe formed of " hardened or indurated 

 mucus," but certainly not the jaw. The presence 

 too of chitin in Mollusca is conceded by all embryolo- 

 gists. It is the first hard substance met with. The 

 shell gland, when first formed, is a chitinous plug in 

 the posterior and dorsal portion in all normal, and in 

 most abnormal forms ; whilst a depression on the 

 dorsal surface of the foot of some Molluscs gives rise 

 to a chitinous plate, the operculum. The whole of 

 these chitinous substances are formed of epiblastic 

 cells, and from similar cells are developed the buccal 

 cavity and oesophagus. The anterior portion of the 

 buccal mass is the jaw, its posterior attachment the 

 oesophagus. 



tion has convinced me that, though a generic idea 

 might be easily set up, yet as a specific classification 

 it would be useless. The variations seem endless. 



In this article I merely treat of one group of land 

 molluscs, Helix nemoralis, H. hortensis, and some of 

 their varieties. As their specific relationship has 

 never been satisfactorily settled, I trust the following 

 notes on the shells and jaws will be a definite step 

 towards that end. 



The group comprised under the above names are, 

 as most naturalists know, those beautifully coloured 

 shells found commonly throughout this country along 

 hedgerows, especially nettle - yielding ones — plain 

 yellow, red, or brown, or encircled with one to six 

 bands. Those with dark coloured mouths are the 

 H. nemoralis ; with white lip and rib, H. hortensis ; 

 and those with a pink lip or rib, H. hortensis, var. 

 hybrida. Amongst the H. nemoralis, characterised as 



Figs. 6 and 7. — H. nemoralis, Leeds (i grown). 



Fig. 9. — H. hortensis, Malton. 



Fig. 10. — H. liortensis, Driffield. 



Fig. 12. — Divisions of 1-100 of an inch. 



Fig. 8. — H. hortensis, var. hybridei, 

 Malton. 



H . hortensis, near Leeds. 



It will (I trust) be clear, that the primitive epidermis 

 or epiblast gives rise in Mollusca to the chitinous 

 parts, and that these are in no case differentiations of 

 mucus. I think we might safely say : — 



That no true horn is found in Mollusca ; 



That cartilage is not found in any of the inverte- 

 brates, except in Cephalopoda, as a support for certain 

 nervous organs in the head, &c. ; 



That chitin forms the shell glands and opercular 

 plates of true Mollusca, the shell valves of articulate 

 Brachiopods, the jaws, &c, of Gastropods, the gill 

 supports and ligaments of Lamellibranchiates (Ano- 

 donta), the gladius and acetabula of the squid 

 (Loligo) and other Cephalopoda. 



It struck me, as far back as 1879, that if the cross- 

 bars of the jaws of snails could be mapped, as the 

 chemist does his spectra bands, one might, by working 

 at a group, make some headway, but micro-examina- 



we have learned by the dark mouth, are sometimes 

 found specimens which agree in every particular with 

 typical nemoralis, except that they possess a white 

 mouth and rib. Every conchologist must have 

 specimens of this kind in his cabinet. For it I propose 

 the name of//, nemoralis, var. albo-labris ; no mention 

 of this, by no means rare variety, being made in 

 " British Conchology." This variety occurs in the 

 Leeds district. 



The varieties hortensis and hybrida of H. nemoralis, 

 as given by Dr. Jeffreys in his " British Conchology," 

 are to my mind a distinct species and its variety. No 

 conchologist yet confused the two. The care with 

 which he handles hortensis, and the admiration that 

 its smaller, delicate, and more graceful form excites, 

 is, to the practical specialist, an intuitive distinction. 

 Perhaps, when the subject becomes better worked, we 

 shall look upon the colour of the lip and rib of var. 



