. April \, 1889] 



NA TURE 



531 



of naturalists. The living animals of the cuttles and 

 squids are remarkably vivacious, as well as cosmopolitan, 

 whilst the Octopus, or "devil-fish," has been invested 

 with quite supernatural powers and intelligence. As to 

 the gigantic calamaries of the North Atlantic, they 

 almost realize in size De Montfort's fancy sketch of the 

 " colossal poulpe " seizing a three-masted ship in its 

 arms ; or the fabled " Kraken," described by Dr. Paullinus 

 and the Bishop of Bergen in the last century as a beast 

 so huge that a regiment of soldiers could conveniently 

 manoeuvre on its back ! 



Striking and varied as are the animals of living 

 Cephalopods, their shells, both recent and fossil, are 

 of immense interest, indeed they are unsurpassed for 

 elegance and variety of form by any of the Molluscan 

 sub-kingdom ; and as we have seldom the other parts 

 left to us— especially in the older rocks— save the shell 

 alone, it becomes necessary to study these structures 

 with increased attention, and strive to elicit from them 

 all that is possible of the past life-history of their in- 

 habitants, and thus, by the light which they afford us, to 

 trace the origin of the allied living forms. 



The labours of naturalists during the past fifty years 

 have tended to eliminate certain groups formerly classed 

 with the Mollusca, and thus to define more clearly the 

 characters of this great phylum of the Coelomata as now 

 recognized. The first group to be reriioved from the 

 Mollusca was that of the Cirripedia by the labours of 

 J. V. Thompson in 1830. In 1866, Kowalewsky showed 

 that the Tunicata had affinities with the Vertebrata, and 

 that their agreement with the Mollusca was only super- 

 ficial. In 1S44, H. Milne-Edwards had placed the 

 Polyzoa with the Brachiopoda and Tunicata in a large 

 group, the '' Molluscoidea" ; but the investigations of 

 Cardwall, in 1882, showed that the Polyzoa and Brachio- 

 poda had only a delusive agreement with the Mollusca, 

 and must be removed from that phylum also. 



There now remain, according to Prof. Lankester, only 

 two great branches of the Molluscan phylum ; namely, 

 (1) the Glossophora (characterized by possessing an 

 odontophore), embracing the Gasteropoda, the Scapho- 

 poda, and the Cephalopoda ; and (2) the Lipocephala 

 (= Acephaia, Cuvier), including all the Lamellibranchiata 

 (mussels, oysters, cockles, clams, &c.), without any 

 definite head. 



The question that interests us most to-day is. To which 

 of the Mollusca belongs the honour of representing 

 the primitive type from which all the varied forms we 

 now recognize have arisen ? Leaving out of consideration 

 the earlier Brachiopoda, as having been already excluded 

 from the Mollusca, we find in the older Palaeozoic rocks 

 that the Pteropoda, Heteropoda, Nautiloidea, and Lamelli- 

 branchiata (or Lipocephala) appear almost contempora- 

 neously. But the Pteropoda (represented by Theca and 

 Conularta), and the Cephalopoda (by Orthoceras sericeum 

 and at least three other species), begin in the Tremadoc 

 rocks ; Lamellibranchs (such as Palcearca and Cteno- 

 donta) in the Arenig ; whilst Gasteropods of several 

 well-marked genera {Mtirchisonia,Pleurotomaria,Euom- 

 phalus, Trochtts, &c.), with Bellerophon and the strange 

 Maclurea, are found in the Bala series. If, as appears 

 from the views of Prof. Lankester, we are to regard the 

 Lipocephala as degenerated forms of Glossophora, they 



I must have begun very much earlier indeed to have 

 I become so differentiated as we find them in the Arenig 

 j group. Nor do the Gasteropoda of the Bala series 

 : present the appearance of primitive forms (unless it 

 ; be the genus Maclurea), for we find moUusks with tur- 

 1 reted, turbinate, and discoidal shells, already defined as 

 i distinct generic types. 



That the Pteropoda preceded the higher Cephalopoda 

 i in time seems pretty certain, and that both of these pre- 

 ceded the Gasteropoda seems established ; but of the 

 priority of the latter over the Lamellibranchiata there 

 is no evidence. 



As Prof. Lankester, in his recent classification of the 

 Moliusca, places the Pteropoda with the Cephalopoda as 

 Branch A. Pteropoda, Branch B. Siphonopoda, we 

 must be content, for the present, to consider that the 

 Cephalopoda represent the most ancient type of Mol- 

 lusca, and that the shells of the little Pteropod, Theca, 

 are the earliest representatives which we at present 

 know. 



In Orthoceras we become acquainted with the first 

 and simplest form of camerated Cephalopod shell. 

 They were straight shells, with plain suture-lines marking 

 the septa, the siphuncle varied in position, the septa 

 being concave towards the aperture ; the initial chamber 

 was conical, with a cicatrix, the body-chamber large, 

 and its aperture simple (pp. 1-128). Nearly 200 species 

 of these straight simple shells are described by Mr. 

 Foord, ranging from the Tremadoc shales of Portmadoc 

 to the Trias of St. Cassian. That they were external 

 shells is proved by their surface-ornamentation, consist- 

 ing of transverse and* longitudinal ridges, and fine 

 decussating striae, with occasional colour-bands and 

 markings rarely preserved. 



In Endoceras (pp. 129-63) the internal structure of 

 the shell is varied by the undulating character of the 

 septa, which bend downwards, and overlap the neck of 

 the preceding septum, forming a complete shelly siphua- 

 cular tube. The siphuncle. moreover, is eccentric in 

 position, and often half the diameter of the shell. With- 

 in this wide siphuncle a series of funnel-shaped conical 

 sheaths (endosiphons) have been observed, of the nature 

 of which we are at present left in doubt. Piloceras has 

 also an unusually large siphuncle, within which a series 

 of invaginated sheaths, similar to Endoceras, occur. 



The genus Actinoceras presents other peculiarities 

 in the structure of the shell. Within the siphuncle, 

 which is very large, a slender tube passes down the 

 centre, called the endosiphon (pp. 164-99). The si- 

 phuncle expands between each septum into a broad 

 bead-like dilatation, perforated around its periphery by 

 a series of minute shelly radiating tubuli given oft' 

 from the endosiphon. It has been suggested by Owen 

 that these were connected with the vascular system of 

 the animal, and were designed to convey nutrition to the 

 lining membrane of the septal chambers. No such com- 

 plex siphon and endosiphon exists in the shell of any 

 living Cephalopod ; nevertheless, it is difficult to accept 

 i for them the interpretation here suggested, unless we 

 ! would invest the shells of these ancient Mollusca with a 

 j structure akin to that of the skeletons of the Vertebrata 1 

 1 The huge siphuncles of Huroma—dWxf^di to Actino- 

 ceras— \ia.s^ been described by Stokes, Bigsby, Hall, and 



