520 Revieics — Professor Watts — Geology for Beginners. 



separation from Argonauta, whilst it further establishes a point 

 of resemblance in this respect between the Ammonoidea and the 

 Nautiloidea. 



The previous literature is scanty. Oppel (1863) figured part 

 of the muscular attachment in Ammonites steraspis, but did not 

 apparently even guess its significance. Trautschold in 1870 figured 

 what he considered to be the impression of the muscular attachment 

 in Ammonites hicurvatus. In 1871 Waagen accepted Oppel's figures 

 as indicating a trace of the annulus, and diagrammatically completed 

 what he considered to be the form of the shell muscle, which he 

 believed was attached to the inner (umbilical) portion of the lateral 

 area of the whorl. In this he appears to have been correct, though 

 Ammonites steraspis proves to be an exceptional form. In the 

 majority of the Ammonoidea the shell muscles were attached 

 to the dorsal portion of the shell : they frequently either met or 

 approximated each other in the median line of the shells, and 

 in the latter case were united by a more or less narrow band 

 corresponding to the dorsal portion of the annulus in the recent 

 Nautilus. They were similarly connected round the ventral side by 

 the annulus, so that an air-tight band fastening the mantle to the 

 shell encircled the animal. Once detected, these scars prove fairly 

 common, and there appears to be some ground for believing that 

 their varying form in the different genera is in part due to the 

 shape of the transverse section of the whorl and to the length of 

 the body-chamber, but also, possibly, to other causes. They will 

 probably ultimately afford important characters for the purposes 

 of classification. 



Mr. Crick describes and figures the pi'incipal forms detected in 

 twenty-eight different genera. He is heartily to be congratulated 

 on the production of this admirable monograph, and the Linnean 

 Society on having published it in worthy form and with adequate 

 illustrations, in which respect they put to shame a younger Society 

 whose complaint is that it cannot get good palseontological papers. 

 What is wanted now is a companion paper summarizing our 

 knowledge of the muscular scars in the Nautiloidea. 



III. — Geology for Beginners. By Professor W. W. Watts, 

 M.A., F.G-.S. 8vo ; pp. xvii, 352. (London : Macmillan & Co., 

 1898. Price 2s. 6cL) 



THE student who nowadays wishes to become a geologist, and is 

 desirous not merely to learn the facts but to aid in advancing 

 knowledge, must labour long and seriously. The general knowledge 

 of rocks and fossils which seemed to form a sufficient basis twenty 

 or thirty years ago, must now be supplanted by a more precise 

 acquaintance with the characters of the principal rock-forming 

 minerals and of the principal forms of life whose remains are 

 found embedded in the strata. The young student should be able 

 to recognize in microscopic slides the minerals and structures 

 exhil)ited by such rocks as granite and basalt, quartzite, statuary 

 marble, and oolite. Precision of knowledge in the beginning is 

 the surest foundation fur subsequent success. In the present; work 



