Hogg, on the Lingual Membrane of Mollusca. 97 



3. Hceniiglossa. (F. 1 — 1 — 1.) 



Murex, Buccinum, Sec. 



4. Rachiglossa. (F. — 1 — 0.) 



Voluta, Mitra, Sec. 



5. Gymnoglossa. (F. oc 0. a .) 



Pyramidella, CanceUai'ia, Sec. 



6. Rhipidoglossa. (F. 00 — 1 — 00) ; or x • — 1 — oc . 



Nerita, Trochus, Sec. 



Dr. Gray invented the term Ctenoglossa for an order which 

 shouUl include the numerous uniform teeth of the Puhno- 

 nata and such like genera, and that of Ctenobranchiata for 

 an entirely new family. In the paper contributed to our 

 own Journal he gives a more complete terminology to his 

 divisions, which he illustrates by figures of the princijjal 

 types. I may add that Mr. W. Thompson described and 

 figured various species of British Helices, Lymnea?, &c., and 

 that Messrs. Ahler and Hancock's well-known ' Monographs 

 on the Nudibranchiata' have made us familiar with some of the 

 peculiarities of the lingual membranes of this most interest- 

 ing family. Some naturalists have proposed to arrange the 

 tongues into four groups, according to the pattern or type of 

 the dentition ; and these again have been made to correspond 

 with the four orders founded by Cuvier, on the character of 

 the branchiae, such as the Pectinibranchiata, the Scuti- 

 branchiata, the Cyclobranchiata, and the Pulmonata. The 

 difficulty in this arrangement appears to be that of retaining 

 some of the species in the orders to which they have been 

 assigned ; for instance, the Chitons wath a gill down each side 

 of the body are evidently out of place among the Cyclo- 

 branchiata. The grouping of animals differing much in 

 their general anatomy, as we see in the Purpura and Buc- 

 cinum, is clearly incorrect. Proceeding, however, with the 

 more special investigation of the tongues of mollusca, it is 

 pretty generally believed that the spines Avhich give so much 

 variety to this organ, although called teeth, are not in reality 

 teeth, or, at all events, not such as we recognise as such in 

 mammals, but rather are corneous and silicated outgrowths, 

 regularly distributed throughout the length and breadth of 

 a muscular ribbon-like membrane, to designate Avhich 

 Huxley proposed the term " odontofore " — tooth-bearing 

 membrane — serving in a vast number of species as an organ 

 of abrasion and trituration or mastication. The outer part 

 of the band and spiny processes being those employed for 

 seizing or securing the food, while those teeth placed in the 

 central portion are used in trituration or mastication. On 



