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Show 1897.] SKELETON OF PELODYTES PUNCTATUS. 583 consensus of opinion (Duges (4), Gb'tte (6), Schulze (18), and others) is that it represents the " basihyal." Not wishing to enter upon an exhaustive and possibly futile discussion of the morphological value of this part, 1 accept the latter determination and call the median plate of cartilage (hh., fig. 1) the basihyal. This median cartilage is connected with two pairs of large lateral cartilages, the so-called " ceratohyals " 1 in front and the branchial plates behind. The ceratohyals (ch., fig. 1) stand out nearly at right-angles to the long axis of the body, and slope but slightly backwards. Their distal ends articulate by an obliquely elongated convex surface (ha., fig. 1) with the under surface of the palato-quadrate cartilage. The internal or mesial extremities are broad and flat, with a delicately curved inner edge, and are united together in front of the basihyal by a broad band of fibrous tissue (the "queres, fibroses Band" of Batlike, 14. p. 132, Pseudis paradoxa ; and the " pars reuniens " of Gaupp, 5, Rana fusca). In front of this is the hyoglossal notch, at present V-shaped, but later semicircular. The branchial skeleton consists of two branchial plates, right and left, attached to the posterior part of the basihyal, and in contact with one another for a short distance in the median line behind it. Each is connected, at about one-fourth of its width from the median line, with the backwardly projecting cusp of the flattened part of the ceratohyal. The small triangular space (s, fig. 1) thus enclosed between the basihyal and the ceratohyal and branchial plate of each side is filled with a loose connective tissue, which only undergoes chondrification in Stage 4. The antero-internal part of each branchial plate is on the same level as the basihyal and ceratohyal, but the remaining grid-like portion of the plate is deeply concave above. The four curved bars, the so-called " ceratobranchials," are directed outwards and backwards and are connected together at their distal end by an irregular marginal band of cartilage (" commissura terminalis " of Gaupp, 5 ; " epibranchiale "of Schulze, 18) and at their proximal ends by the common hypobranchial plate (hbr., fig. 1). The distal halves of the ceratobranchials bear on their anterior and posterior surfaces a series of four or five irregular, short, blunt outgrowths of 1 I fail to see the practical utility of the introduction by Gaupp (5) of new non-committal terms, such as byale, branchialia, and planum branchiale. It i s doubtful, most anatomists will admit, whether the structures so designated correspond exactly to the ceratohyal. ceratobranchials, and hypobranchials of the fish, and it would have been desirable if, in the first instance, less definitive terms had been employed until the true homologies of the parts had been determined. But n ow that the names have been in use for so long and are so familiar, it is only confusing matters to attempt to replace them by names more vague in their significance. When the implied homology has been definitely disproved, when the so-called ceratuhyal of the tadpole has been shown to be something quite different from the ceratohyal of the fish, and so on, then will be the time for a radical change in our nomenclature. W e are, however, still in the dark with regard to the morphological significance of the Anuran byobranchial skeleton, and the onus of the proof of the false homology implied by the terms at present in use lies with the objectors. |