Analy Ileal Notices. 121 



carnivorous Trachelipodes iii the formation above the chalk, Mr, 

 D. thinks that the vast and sudden decrease of one predaceous 

 tribe, has been provided for by the nexa creation of many genera, 

 and a myriad of species possessed of similar appetencies, and yet 

 formed for obtaining their prey by habits entirely different from 

 those of the Cephalopodes. 



Small circular holes bored in shells by the predaceous Trache- 

 lipodes, so common among recent shells, and also not unfrequent 

 among the fossils, but to be seen only in those of tertiary forma- 

 tions, suggest to Mr. D. the probability that the Aporrhaides* and 

 other fossil Trachelipodes, that occur in secondary formations, 

 though really carnivorous, were in the habit of feeding only on 

 dead animals. We do not think this altogether confirmed by 

 fact, for in the green sand, the newest (we believe) in which the 

 Aporrhaides occur, many of the bivalves are pierced exactly in 

 the same manner as by the carnivorous Trachelipodes : at the 

 same time we ought to remark, that the general contents of the 

 green sand, are such as would warrant the supposition, that its 

 formation was anterior to the generality of tertiary formations, 

 and posterior to the secondary, inasmuch as it contains Ammo- 

 nites as well as carnivorous Trachelipodes. We think the 

 Scientific Enquirer would be amply repaid for the trouble of 

 pursuing the subject of Mr. Dillwyn's paper. 



[The three following notices are extracted from the " Memoires 

 de la Societe d'histoire naturelle de Paris." We reserve the ac- 

 count of two other papers contained in the same volume, (" On 

 the Geology of the Environs of Antwerp," and " on the Genus 

 Melanopsis," for another opportunity.] 



Memoir on Branchiobdella, anew Genus q/*ANNELIDES 

 oflhefamilj/ HinuDiMEiE, bi/ M. Aug. Odieu. 



The animal which forms the subject of this Memoir is parasitic, 

 and was found on the braiichias of the Crayfish. The generic 

 characters assigned to it are as follows : — 



* From Aporrhais, a gentric iiinne given by Petiver to the (ftrombus Pes- 

 rtlecaiii. Linn. 



