1865.] Geology and Pakeontology. 103 



the Zone of Avicula contorta to belong to the Lias, and that the 

 German and English authorities find it more convenient to treat of it 

 as a separate formation ; but believe it to have a closer relationship 

 with the Trias. 



We have said enough to show that Geologists who have specially 

 studied the subject are by no means agreed as to the best way of solving 

 the difficulty ; but the memoirs we have quoted all contain much 

 valuable matter, independently of their bearing on this question. M. 

 Benevier's paper contains a discussion on the exact meaning of the 

 term Infra-lias, and he shows that it includes two sets of strata, which 

 are perfectly distinct from one another in the region of the Vaudois 

 Alps ; for the lower zone he retains the name of Ehaatic beds (Etage 

 Bhetien), but for the upper he proposes that of Etage Hettangien. 

 M. Deslongchamp's memoir is especially remarkable as containing a 

 proposal to separate the Upper Lias of Normandy altogether from the 

 Lias-formation, and to incorporate it with the Lower Oolite (Systeme 

 Oolithique Inferieur), under the name of "Marnes Infra- Oolithiques," 

 and in association with the Inferior Oolite, the Fullers' Earth, and the 

 Great Oolite. This change, if adopted, would shift a battle-ground, 

 which has hitherto been the " Upper Lias sands," or " sands of the 

 Inferior Oolite ;" but we doubt whether it will be generally accepted, 

 and if accepted, whether matters would be improved thereby. 



All the papers mentioned contain valuable lists of fossils, sections 

 of strata, and detailed descriptions of the rocks in the several dis- 

 tricts. 



Professor Huxley's monograph " On the structure of the Belemni- 

 tidoz" has just been published in the Memoirs of the Geological 

 Survey, and clears up many points in their organization that have 

 hitherto remained more or less obscure. One magnificent specimen 

 of a Belemnite, in the collection of the Eev. Mr. Montefiore, exhibits 

 not only the guard, phragmacone, and pen, but also the general con- 

 tour of the body, the beak, and some irregular lines of hooks indi- 

 cating the position and extent of the arms. This is the most complete 

 Belemnite ever found, and we therefore reproduce a reduced copy of 

 the figures of it, illustrating Professor Huxley's description, especially 

 as it gives us, with the author's aid, a clear insight into the structure 

 and organization of the creature. 



Amongst the many new points contained in this monograph, we 

 must confine our attention almost entirely to one, namely, the system- 

 atic importance given to that rarely preserved organ which has hitherto 

 been known as the " pen " or " osselet," but to which Professor Huxley 

 has given the name of pro-ostracum, to avoid ambiguity, as he con- 

 siders it to correspond to only a part of the structure known as the 

 " pen " in recent Cephalopods. This osselet has always been a small 

 bone of contention with naturalists, and the author, after a careful 

 review of the works of previous writers on the subject, gives the 

 following summary of their opinions : — 



" 1. According to Dr. Buckland, this part is a corneous, or shelly, 



