532 



NATURE 



[April /^, 1889 



Woodward (pp. 199-207). The septa and shell- wall are 

 thin, and but rarely preserved. These weathered tubes 

 were frequently noticed by Dr. Bigsby standing out in 

 relief from the limestone clififs of Drummond Island on 

 Lake Huron, and were as large as the vertebra of a man, 

 and not unlike them in shape, and over 6 feet in length. 



In the family of the Gomphoceratidce (pp. 211-45), we 

 meet with shells ranging from nearly straight, through 

 varying degrees of curvature, to one in which a complete 

 whorl is attained. The aperture of the shell in this 

 family is so contracted that it is obvious the animal could 

 not have withdrawn its head into its body-chamber as 

 does the living Nautihcs. The mouth of the shell is 

 T-shaped, and reminds one of the mouth of the shell 

 in some land-snails, like Helix globulosa and Auricula 

 scarabcEus, which are so guarded by tooth-like projections 

 from the margin of the aperture as seemingly to preclude 

 the animal from ever retreating into its shell, or emerging 

 from it if withdrawn. 



The AscoceratidcB (p. 246) have the test of a sac-like 

 form, the body-chamber extending to the lower end of the 

 dilated portion of the shell, while the septa adhere to the 

 dorsal wall, and bend upwards with their convex side 

 towards the mouth of the shell. The apex was unknown, 

 the shell being always found truncated, but Barrande^ 

 first, in Bohemia, and subsequently Lindstrom in Sweden, 

 have discovered the earlier apical portion of the shell of 

 Ascoceras, which was nearly straight, and with the septa 

 normal, as in Orthoceras (p. 335). 



The Cyrtoceratidce (pp. 262-318) are more regular in 

 their growth than the preceding ; the shell is more or less 

 curved, and tapers rapidly, or more slowly, according to 

 the species or variety examined. The siphuncle is small, 

 and varies in position in the different species, being 

 external, internal, or sub-central ; they range from the 

 Carboniferous to the Tremadoc series, and are well 

 represented in the Devonian of Gerolstein, Eifel, by 

 large and handsome forms. 



In his introduction the a ithor discusses many points of 

 great interest relating to the class, as, for example, the 

 classification, the structure of the shell, the range in 

 time, and the distribution of the group. 



Seventeen genera and 403 species are described, but 

 there yet remain the Lituitultr, Trochoceratidce, Nautilidce, 

 and Bactritidce, to complete the Nautiloidea ; while the 

 Ammonoidea and the Dii^ranchiata will be treated 

 of still later on. 



Mr. Foord writes : — - 



" The classification of the Nautiloidea adopted in this 

 volume will be found to differ in some of its details from 

 systems hitherto employed, the more recent writings of 

 Noetling, Zittel, Mojsisovirs, and Hyatt having furnished 

 the basis of the changes mtr iduced. The arrangement of 

 the groups described in th' following pages is primarily 

 zoological, secondarily strati graphical, each genus being 

 dealt with separately, from i; ^ ippearance to its extinction." 



The author passes in nv ew the various systems of 

 classification of the Cepiia opoda proposed by Prof. 

 Hyatt, Dr. Paul Fischer, 1 ; irrande, and other writers 

 on this group. 



" Hyatt considers that 

 Gyroceras, Lituites, Naul 

 terms for the different sta 



eneric terms Cyrtoceras, 

 ire merely ' descriptive 

 I the development of an 



individual, and also the different stages in the develop- 

 ment or evolution of the adult forms in time. In other 

 words, each of these genera, as now used, includes repre- 

 sentatives of all the different genetic series of Tetrabranchs, 

 which are either young shells in the corresponding stage 

 of growth, or adult shells in the corresponding stage 

 of evolution.' He finds ' that genetic affinities on a large 

 scale are best exhibited by the siphuncle, particularly by 

 the funnels of the septa, which are more invariable than 

 any other part of the shell.' 



" He next discusses the embryonic relations of the 

 structure of the septa and of the siphuncle, and mentions 

 the difference between the Nautiloids and the Ammonites 

 exemplified in these structures, the one commencing with 

 a globular initial chamber (' protoconch ' of Owen), the 

 other with a conical initial chamber and a cicatrix. He 

 remarks that generally among the Palaeozoic Cephalopod 

 types much greater differences exist, in regard to the 

 septa, the position of the siphuncle, and so on, than 

 among the Mesozoic forms, thus indicating that the evo- 

 lution of forms was quicker in the Palaeozoic epoch than 

 at subsequent periods, and from these circumstances he 

 concludes that ' types are evolved more quickly, and ex- 

 hibit greater structural differences between genetic groups 

 of the same stock, while near the point of origin, than 

 they do subsequently.' It must not be forgotten, how- 

 ever, that the Palaeozoic epoch was of much longer dura- 

 tion than the Neozoic. ' In the smaller divisions (families 

 and genera) of Hyatt's scheme of classification, an im- 

 portant place is assigned to the characters of the sutures 

 for distinguishing the different groups. In some groups, 

 however (notably the Orthoceratidae), the less stable cha- 

 racters presented by the ornamentation of the shell are 

 for a like purpose employed.' 



" While there can be no question as to the value of 

 Prof. Hyatt's work, and the thoroughness of research 

 which he has brought to bear upon the class he has with 

 so much boldness and originality attempted to re-classify, 

 the extremely revolutionary nature of the changes he has 

 proposed in the minor divisions of his system (involving 

 the wide separation of many forms hitherto associated 

 together) challenges the inquiry as to whether our know- 

 ledge of the developmental history of the Cephalopoda 

 is not as yet far too imperfect to justify such a radical 

 departure from existing systems. The suppression of the 

 familiar names Cyrtoceras and Gyroceras seems quite un- 

 necessary, and seeing that the names Orthoceras and 

 Nautilus are retained, in a restricted sense, in Hyatt's 

 scheme, there seems to be no good reason why the two 

 former should not have been similarly used " (Introduction, 

 p. vii.). 



Mr. Foord discusses at some length the nature of the 

 camerated structure of ^the Cephalopod shell, and the 

 question as to whether the catnera should be called " air- 

 chambers " or " water-chambers " ; he concludes to avoid 

 the difficulty by calling them " septal chambers." Bearing 

 in mind the fact that each sealed-up chamber of the 

 shell is but the partitioned-off lower portion of the ani- 

 mal's body-chamber, it is obvious that it must, at the 

 moment of separation, contain the same medium as that 

 which envelopes the animal. 



In the case of the living Nautilus, dredged by the 

 Challenger o^ Matuku Island, in 320 fathoms,^ it seems 

 improbable that the " septal chambers " could have been 

 full of gas when the animal was crawling upon the sea- 

 bed at a depth at which the pressure would be equal 

 to about 750 pounds on each square inch of surface, or 

 fifty-three times greater than at the sea-level. Any such 



I See " Notes of a Naturalist on the Challenger," by H. N. Moseley, 

 M.A., F.R.S. (p. 297)- 



