Mevietvs — ReliquicB Aquitanicce. 321 



form, as well as in its anchylosed segments, it differs remarkably in 

 ha-sdng the area enclosed by its eye-ridge (glabella) comparatively 

 small, and of a quadrangular form, with the eyes situated far for- 

 ward at its anterior lateral angles. — Amer. Jour. Science, and Arts, 

 May, 1867. 



laiEAT'IiE'SAT'S. 



I. — Eeliqui^ Aquitanic^. : Being contributions to the Akch^o- 



liOGT AND PALiEONTOLOGT OF PeRIGORD, AND THE ADJOINING PRO- 

 VINCES OF Southern France. By Edouard Lartet and Henrt 

 Christy, Edited by Professor T. Eupert Jones, F.G.S., etc., etc. 

 (Third Notice.) 



IN referring again to this important work we have only to state that 

 Part IV. maintains the high character for which the three pre- 

 vious Numbers were distinguished. The six plates now issued 

 are devoted to figures of stones, used as mortars, to flint cores from 

 which flakes have been struck, and to a further series of cleverly- 

 carved Eeindeer-horn weapons. The figures of animals, engraved 

 upon some of these remains, possess great merit; especially we would 

 notice the carving of a deer on B. PI. vii. et viii., fig. 6. 



Chapter III. is devoted to a notice of the chief Geological features 

 of the valley of Vezere, and the bordering country, accompanied by a 

 sketch-map and section of that valley. 



As suggestive of the origin of flint in the Chalk of the Dept. 

 de la Dordogne, the Editor considers (p. 32) that it is only so much 

 of the Cretaceous stratum silicified. 



"The particles of Polyzoa, the Orhitoides, and other organic remains 

 being still in place, and retaining their characteristic structures. 

 Even fish-teeth (Otodus) have been altered into flint except a thin 

 external pellicle." " There is also flint showing a further progress 

 of mineralization, in which the constituent organic remains of the 

 limestone have been more and more removed from sight by the 

 increased homogeneity of the pseudo -amorphous silex, as is usually 

 the case with the flint of Northern Erance and England." 



That some flint may have been so formed is possible, but it is 

 equally probable that many, if not all, the flint nodules and bands 

 occurring in the Chalk and even chert, owe their origin to a segre- 

 gation of silicia, previously held in solution — around some nucleus — 

 such as a silicious sponge, or other organic remain, which almost 

 invariably accompanies these bodies. 



We imagine the author would not include in his list of pseudo- 

 morphic silicious replacements, the fissures filled with flint in the 

 Chalk as at Pegwell Bay, in Kent, and Eottingdean, near Brighton, 

 and many other localities, which are not unfrequently lines of fault. 

 These veins of flint seem to justify one in attributing their occun'ence 

 to the simple infiltration {without replacement) of the Silica. 



■VOL. IV. NO. XXX.VU. 21 



