J. E. GRAY. 587 



group, situated between the Chiton and Patella. According 

 to Deshayes, on whose authority the order Cirrhobrancluata 

 solely rests, the brancliia3 in Dentalium are grouped in the 

 form of two tufts of long soft filaments with clavate extre- 

 mities, one on each side of the animal's neck ; but Mr. 

 Clark appears to have proved that these organs are really 

 salivary glands : so that the usually accepted view of the 

 cirrho-branchiate character of Dentalium becomes unte- 

 nable.* 



In 1842, or earlier, Mr. J. E. Gray proposed a very mate- 

 rial modification of Cuvier's arrangement ; f and the differ- 

 ences between them will be made most obvious by reducing 

 Mr. Gray's method to a tabular form. The Gasteropoda 

 then are — 



I. CTENOBRANCHIATA with the respiratory organs 

 consisting of one or more comb-like gills placed on the 

 inner side of the mantle, which forms an open bag in 

 the last whorl of the shell, over the back of the neck. 

 Order I. Zoophaga, embracing five families, viz. — 

 1. Strombidae ; 2. Muricidae ; 3. Buccinida? ; 

 4. Volutidae ; 5. Cyprseadse. 

 Order II, Phytophaga. 



Section I. Podophthalmi. 

 Eyes placed on short pedicels at the back inner angle of 

 the tentacula. 



* Sides of the body furnished with a fringe sending out a 



series of tentacvilar filaments. 



The families are 1. Turbinidae ; 2. Trochidse ; 3. Stoma- 

 tellidae ; 4. Haliotidae ; 5. Fissurellidae ; 6. Denta- 

 liadae ; 7. Lottiadae. 



*■* Sides of the body destitute of fringe and filaments. 

 Tentacula generally elongate and slender. Shell inte- 

 riorly always opake and porcellaneous. 



The families are 1. Neritidae ; 2. Ampullariada? ; 3. lan- 

 thinidee ; 4. Atalantidae. 



Section II. Eriophthalmi. 



Eyes sessile, or only placed on a very small prominence at 

 the base of the tentacula : sides simple. 



* Branchiae formed of triangular plates and not exposed : 



shells generally regularly spiral with a moderately 

 sized aperture. 



* Forbes and Haiiley Brit. Mollusca, iii. 447. jMr. Clark's very interest- 

 ing paper is in the Ann. and Mag. Nat. Hist. Ser. 2, iv. 321. 



+ Synopsis of the Contents of tlie British Museum. Lond, 1842. Duud. 

 — Mr. Gray states that liis method was first published in 1838. Proceed. 

 Zool. Soc. No. 178, p. 129. 



