132 



ings. He gives in each case a particular account of the mode of 

 dissection, with a view to direct succeeding observers to obtain a 

 distinct view of the parts he describes, and to verify the conclusions 

 he has himself obtained. 



He next notices a considerable modification in the structure of 

 these organs which is presented in the Chiton. In this animal he 

 finds a pair of simple lateral jaws, rather membranous than cartila- 

 ginous. Another variety of structure adapted for gorging food is 

 met with in the Patella mammillaris, where there is simply a very 

 muscular mouth and pharynx, but neither cartilage, tongue, nor 

 hard part of any kind. 



The apparatus by which the Buccinum Lapillus drills through shells 

 in order to obtain its food, and the process it employs for that pur- 

 pose, are next investigated ; and that of the Buccinum undatum is 

 particularly examined with the same view, the structure of the latter 

 being very fully displayed. 



The author hopes to be enabled to pursue these inquiries with 

 respect to other tribes of Mollusca at some future period. 



6. " On the Mammary Glands of the Ornithorhynchus paradoxus," 

 by Richard Owen, Esq. Communicated by J. H. Green, Esq., F.R.S. 



The author premises a history of the different opinions that have 

 been entertained with respect to the anatomy and economy of this 

 singular animal, which was first described and figured by Dr. Shaw 

 in the year 1792. The name of Ornithorhynchus, which it at present 

 bears, was given to it by Blumenbach; and some account of the 

 structure of the head and beak was given in the Philosophical Trans- 

 actions by Sir Everard Home in 1800; and in a subsequent paper he 

 states his opinion that this animal differs considerably from the 

 true mammalia in its mode of generation, an opinion which was 

 adopted by Professor Geoffroy St. Hilaire, who accordingly placed 

 it, together with the Echidna, in a separate order designated by the 

 term Monotremes. He afterwards formed this group into a distinct 

 class of animals, intermediate to mammalia, birds, and reptiles. Oken 

 and De Blainville, on the other hand, condemned this separation ; 

 and maintained that the monotremata should be ranked among mam- 

 malia, and as being closely allied to the marsupialia; and hazarded 

 the conjecture that they possessed mammary glands, which they ex- 

 pected would ere long be discovered. Professor Meckel has since 

 described these glands as being largely developed in the female 

 Ornithorhynchus. He considers this animal, however, in the mode of 

 its generation, as making a still nearer approach to birds and rep- 

 tiles, than the marsupial tribe. He was unable to inject these glands 

 in consequence of the contracted state of the ducts arising from the 

 action of the spirit in which the specimen was preserved, and from 

 their being filled with a concrete matter. Geoffroy St. Hilaire, in a 

 subsequent memoir, persists in denying that these bodies possess the 

 characters of mammary glands ; but regards them as a collection, not 

 of acini, butot coeca, having only two excretory orifices, and present- 

 ing no trace of nipples. 



The author of the present memoir, having examined with great 



