180 liVRMA. ITS I'KiiPl.K .l.V/> rnODCCTIOXfi. 



to form a sort of g;rapiicl, to ■\vliicli a perforated iloinc is attaclied, answering tlie 

 purpose of a sinker. The basket is now -weifrlited with stones, well baited with 

 boiled crayfish {I'alinurm), suggested no doubt by the large quantity of tlic fragments 

 of cnistacea usually to be found in the crop of the Nautilus, and then dropped 

 gently down near the victim. The trap is now either closely watched, or a mark 

 is placed upon the spot, and the fisherman pursues his avocations on other parts of 

 the reef until a certain period has elapsed, when he returns and in all probability 

 finds the NautUus in his cage feeding on the bait." 



The shells of Cephalopoda are either internal, like Spirtda and Bekmiiite.t, or 

 external, like ^"aiitilus and Ammonites. They may be either straight, like Ortho- 

 ceras, involute, like Spirilla, or rcvolute, like Xaidilus and Ammonites. The term 

 involute, or ' curled under the belly,' and revolide, or ' curved over the back,' are 

 used with reference to the back and belly of the animal. On this subject great 

 misapprehension has universally prevailed, and the terms ' ventral ' or ' dorsal ' 

 have been applied to the shell without regard to the position it held quoad 

 the ventral and dorsal aspects of the animal. A masterly paper by Professor 

 Owen (in Proc. Zool. Soc. Loud. 1878, p. 955) cleaily shows how erroneous 

 the popular nomenclature is, and the following passage definis the true sense 

 in which the terms dorsal and ventral should be used in respect to the Cephalo- 

 poda ; — The dorsal aspect of a Cephalopod is determined by the position of 

 the brain and eyes, i.e. by that predominating part of the brain which sends off 

 the optic nei-ves. The ventral aspect is shown by the respiratory funnel. No 

 malacologist has questioned these conclusions. The proposition might be simplified 

 by stating that the funnel shows the 'ventral side' of the animal, and that the 

 opposite one is the ' dorsal side.' To give a familiar application of this mode of 

 viewing the shell of a Cephalopod, we have only to imagine a dog's tail as represent- 

 ing the curled siphuncle of the shell. In a terrified condition of mind, its tail will 

 be coiled under its belly, or involutely, and will then represent the curve of the 

 Spirula, quoad the position of the animal ; but when in a jo}-ous fi-ame of mind, 

 its tail will be curled jauntily over its back, or '■ revolutehj^ as is the curve of 

 Nautilus as regards the animal which formed the shell. This explains a seeming 

 anomaly thus described by Owen {I.e.'): "Accordingly, all who have occupied 

 themselves with the organization of the Cephalopods have pointed out the singular 

 reversed positions of the mandibles, as compared with those in such vertebrate 

 animals as repeat the cephalopodic condition of a 'beak,' as e.g. Clielunia and Ares. 

 Instead of the dorsal, or upper mandible, being the largest and longest, so as to 

 overlap the ventral, or under mandible, as in birds, the dorsal mandible is the 

 smaller and shorter, and is underlapped by the larger and longer ventral mandible 

 in all Cephalopods." Of course the real state of the case is, that the beaks of a 

 Cephalopod are really precisely homologous to those of a hawk, the upper, or dorsal, 

 overlapping the lower, or ventral, but these terms having been erroneously applied 

 to the shell, the ' beaks ' of the Cephalopod have seemingly (but not truly) displayed 

 the above curious deviation. It is therefore an error to use the terms 'donal' and 

 'ventral' as synonymous with 'external' and 'internal,' as is so generally done. Of 

 course, in all coiled shells, the convexity is external, and the concavity internal, 

 and there is no objection to ap])lying these terms to the shell; but when we speak 

 of ventral and dorsal, we must then have regard to the animal, and discrimination 

 is then imperative, whether the shell is dorsally rcvolute, or vcntrally involute, our 

 sole guide being, of course, the relation of the shell to the ventral and dorsal aspect 

 of the animal. 



Order DEC.VPOD.V. 



Limbs (amis) ten. An internal shell. Two of the arms arc elongated and fitted 

 with pedunculated cups. The decapods are divided into Vhoudrofihura with an 

 internal hf)rny pen ; Sepiophnra with a calcareous bone ; and Belemnopliora with an 

 internal chambered shell. The size to which some members of this order grow may 

 be gathered from the size of an Arehiteuthis princeps, Packard, which was en- 

 countired by some fishernum in Conception Bay, Newfoundland, and which is 



