OCR Text |
Show MR. C. TATE REGAX OX [Nov. 4, the barbs of the dorsal spine, if distinct, are usually in four series. There are 19 or 20 vertebrae. In this genus the gradation is perfect from those species without barbs to those with four equidistant series of strong barbs. G. A l u t e r a C u v .- Differs from Pseudomonacanthus in that the dorsal spine is feeble, the ventral spine is absent, the pelvis is entirely concealed, and the dorsal and anal rays usually in greater number. The lower jaw is projecting, the gill-openings oblique and below the eye, and the vertebrae number 21. 7. P siloc epha lu s Swainson.-Differs from Alutera in its more elongate body, very feeble dorsal spine, lower jaw with a barbel, gill-openings in advance of the eye, and vertebrae numbering 29-30. This family has well-defined characters, and the relations of the various genera are very clear ; its division into subfamilies is without value, and if Balistes and Psilocephalus are to rank as distinct families, Monacanthus, Alutera, Paraluteres, and Pseud-aluteres should receive the same treatment, and the Balistidae (as here understood) be raised to the rank of a division. Some authors have stated that the symplectic is not ossified in the fishes of this and the next family. I find that in all cases it is present as a small but distinct ossification attached to the lower margin of the metapterygoid between stylo-hyal and quadrate; the stylo-hyal has shifted its attachment forwards from the hyo-mandibular to the anterior part of the lower margin of the metapterygoid, and has, as it were, pushed the symplectic in front of it. Family 4. O s t r a c io x th l e . Closely allied to the Balistidae, but with feeble parapophyses, no epipleurals, praeorbital not ossified, palatine immovable, pelvis absent, no spinous dorsal, no ventrals, soft dorsal and anal short. Clavicles, coracoids, and post-clavicles much expanded. Scales represented by large, juxtaposed, bony plates, mostly hexagonal and immovably united. Genera. 1. Aracaxa Cray.- Body ovate or orbicular. Carapace ceasing before the dorsal and anal fins, with more or less distinct longitudinal ridges, 3 on each side, and often a dorsal and ventral ridge; some isolated plates on the caudal peduncle. D. 10-12. A. 10-12. Caudal truncate or rounded. Sixteen vertebrae, not elongate, subequal in length except the two preceding the square hypural, which are shortened. 2. Ostraciox Linn.- Body 4- or 5-sided; carapace extending beyond and closed behind the anal fin, with two prominent ridges <m each side and often a dorsal ridge. Caudal peduncle naked. I). 9-10. A. 9-10. Caudal truncate or rounded. Sixteen |