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Show 1,889.] ANATOMY OF GONATUS FABRICII. 125 nearly that of Ommastrephes, of all those which have hitherto been described in detail \ The brachial ganglion (br.g.), however, is not quite so widely separated from the pedo-visceral (p.v.) as in that genus. The fusion between the pedal and visceral ganglia is very complete. Buccal ganglia (b.g.) are situated upon the posterior extremity of the buccal mass, and are connected as usual both with the cerebral and brachial ganglia. Furthermore there is present a cerebro-bra-chial connective. The Peripheral nerves could scarcely be made out at all owing to the disintegrated condition of the specimens, but it was easy to see that the brachial commissure is simple as in all Decapoda. The Stellate ganglia are large flattened pyriform bodies ; they are connected by a strong and easily recognized commissure. The pallial nerve (p.n.) divides a little distance before reaching the ganglion, the main trunk passing directly backwards and reuniting with the nerve given off from the posterior extremity of the ganglion. This arrangement resembles in its general features that figured by Brock 2 for Ommastrephes and Todarodes, but with certain minute differences. A number of sections were made of the Eye, but they did not exhibit any features calling for special notice. The Osphradium consists of a small antero-posteriorly directed ridge, which is placed below and a little behind each eye; it could be very clearly followed through a number of sections extending perhaps over half a millimetre of the animal's length. The preparations did not show any of the histological features characteristic of the osphradium, but I feel justified in regarding this ridge as such partly because of its position, and partly because just internal to each of these ridges there was a foramen in the cephalic cartilage through which passed a nerve. The Auditory Organs occupy their usual position. VII. Digestive Organs. The Beak is remarkable chiefly for the long curved apex of the superior mandible. It has been figured by Steenstrup, but unfortunately the plate containing it has not yet been published. The Radula has been admirably figured by Sars3. It is remarkable as being the only known Cephalopod radula in which only five rows of teeth are present. On comparing it with the radulse of Onychoteuthis 4 and Enoploteuthis 5 it appears that the teeth which have disappeared are those situated close to the median tooth (" Zwischenplatten " of Troschel). The median teeth themselves have a long median denticle, and on either side a short acute denticle, so that they resemble those of Onychoteuthis rather than of 1 Compare Pelseneer, " Valeur morphol. des bras, &c. . . . des Ceph.," Arch. de Biol. viii. fig. A. 2 Brock, op. cit. p. 226, pi. xi. fig. 7. 3 ' Mollusca regionis arcticce Norvegite,' pi. xvii. fig. 2 (1878). 4 Troschel, " Mundtheile d. Ceph.," Arch. f. Naturg. xix. i. p. 11, pi. i. fig. 6. 5 Brock, op. cit. pi. xii. fig. 10 C. |
