de la Faimc de Cula. YO 



cle la pectorale ; les plus petites sont snr la region jugulaire. II 

 y en a de tres-petites snr la base des nageoires vertical es. II 

 n\y en a pas sur I'interopercule ni sur le museau. — N° 390. 

 Yoyez les autres caracteres dans la famille et le genre, 

 L'original sera envoye an Professenr Agassiz, pour etre 

 depose au Museum de Cambridge. 



IV. — 0)1 the Lingual Dentition of Helix turhiniformis^ ^*f'*^-i 

 and other' sjyecies of Terrestrial MoUnsca. 



By THOMAS BLAND and W. G. BINNEY. 



Read May 15th, 1871. 



Helix tiirbiniforiui^, Pfeiffer. 



(Plate II., Fig. 2.) 



Jaw so extremely thin and delicate as to fold over upon itself 

 along its edges and at its extremities ; very light horn color, 

 almost transparent ; strongly arched, rather narrow, attenuated 

 towards the ends, which are obtuse ; divided into about forty 

 separate perpendicular compartments composed of curving fold- 

 like plates, whose extremities give a correctly serrated appear- 

 ance to either margin ; these plates or folds are straight at tlie 

 centre of the jaw, and in no wise clievron-shaped upon the 

 central line; upon about the centre of the jaw is a curving, 

 horse-shoe shaped line of reinforcement, running somewhat 

 parallel to the margin, below this line there are very delicate 

 transverse strise ; the upper margin is slightly incurved at its 

 centre, the lower margin has no approach to a median pro- 

 jection. 



It is difficult to determine the precise nature of the fold-like 

 plates into which this jaw is divided. They give the same ap- 

 pearance as if the whole substance of the jaw were plaited along 



JULY, 1871. 6 Ann. Lyc. Nat. Hist., Vol. X 



