Reviews — The Palceontographical Society. 83 



Then follow descriptions of various tail-pieces belonging to the genus 

 Dithjrocaris ; some remarks upon the allied genus Mesothyra from 

 the Devonian strata of North America, and a note upon F. A. Eoemer's 

 Ditliyrocaris Jaschei from the Hercynian Limestone in the Kloster- 

 holz, near Ilsenberg, Hartz, which the authors refer with a query to 

 the genus PtycJiocaris. There is a short chapter on " The Gastric 

 Teeth oi Dithyrocaris," with a number of illustrations of these curious 

 little fossils. The part concludes with observations on " Some Allies 

 of Dithyrocaris." These are — (i) Lehescontia isnigmatica, a. new genus 

 and species founded upon two specimens which were collected by 

 M. Paul Lebesconte, of Rennes, from the Lower Silurian rocks of 

 Brittany and neighbourhood, which, although " somewhat obscure 

 on account of imperfection, distortion, and embedment," the authors 

 believe to be " the relics of some kind of bivalved or shield-like 

 Phyllopod, near to but not identical with Ditliyrocaris" ; (ii) 

 Lehescontia occulta, a new form from the " Upper Limestone " 

 series at Linn Spout, south-west of Dairy, twenty miles south-west 

 of Glasgow; (iii) Hibbertia orbicularis, already described and figured 

 by the authors in the Geological Magazine for September, 1899. 



This being the concluding part of the Monograph there are various 

 lists, several pages of " Addenda et Corrigenda," and an index and 

 general title-page to the whole volume. The binder is instructed to 

 " cancel the title-pages of parts i, ii, iii, and iv , . . and substitute 

 the general title-page given in the volume for the year 1899 " ; but 

 though the dates of the several parts are given, some workers may 

 prefer to have the volume bound with the title-pages of the several 

 parts in position as issued. We shall certainly do so ourselves. ^ 



2. A Monograph of the Cretaceous Lamellibranchia of England. 



By Henry Woods, M.A., St. John's College, Cambridge. 



Part I : Nuculanidee, Nuculidas, Anomiidae, and Arcidge. 



pp. 1-72 : pis. i-xiv. 

 Mr. Woods has already devoted much attention to the Palaeontology 

 of the Invertebrata, and not very long ago contributed to the Geo- 

 logical Society of London an important paper on " The Mollusca of 

 the Chalk Rock" (Q.J.G.S., vol. Iii, 1896, pp. 68-98, pis. ii-iv; 

 and ibid., vol. liii, 1897, pp. 377-404, pis. xxvii and xxviii). 

 Mr. Woods doubtless found the nomenclature of the Cretaceous 

 Lamellibranchiata in a sad state of confusion, and this may have led 

 him to commence the present Monograph. The bad state of pre- 

 servation of many of the Chalk Mollusca renders their study 

 exceedingly difficult ; but as the Chalk is now attracting the special 

 attention of not a few geologists, it is very desirable that all the 

 Mollusca, especially the Lamellibranchiata and the Gasteropoda, which 

 have hitherto been in a very unsatisfactory state, should be over- 

 hauled, and the nomenclature corrected as far as possible. Mr. Woods' 

 monograph appears, therefore, very opportunely, and he deserves the 

 hearty thanks of all for undertaking to work out this very difficult 

 group. As in every other group, many species have been very 

 differently interpreted by different authors ; we are therefore glad 

 to find that whenever possible the type-specimens of the species 



