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Show 586 PROF. G. B. HOWES ON T H E C O R A C O I D [June 20, Edentates alone excepted) either abuts against or is confluent with the scapular element, and its acromion when differentiated1. It is thus seen that the same term has been applied to a localized outgrowth of the coracoid element most variable in its differentiation, and to a distinct element of invariable relationships. The different usages of the term epicoracoid have been productive of a precisely similar confusion, as I have elsewhere pointed out2. If, as is most desirable in the progress of anatomical science, distinct substantive names are to be applied to distinct structures, the terms precoracoid and coracoid must in the future be used to distinguish a portion of the ventral half of the shoulder-girdle which is from one which is not related to the clavicle. Upon this principle the term epicoracoid can only apply to the M a m malia, aud those Anomodontia 3 in which the coracoid is segmented into two perfectly distinct parts which ossify independently. In commenting upon m y proposal to restrict the term epicoracoid to the element so named by Cuvier in the Monotremes and its serial homologue, and the term precoracoid to the cartilaginous clavicular bar and its representative, M r . Lydekker remarks that " this emendation, if properly authenticated," he would have been willing to accept. I presume that by " properly authenticated " he means tenable upon the accepted rules of priority in nomenclature ? If so, I would ask what would be the outcome of the application of these, with their rigid restrictions, to the terminology of, say, the elements of the carpus and tarsus, or the muscles of the limbs, so variable in both their characters and detailed relationships? Confusion worse confounded, ' progress' but not scientific advancement, would, I venture to think, ensue. Having proposed to reject the term epicoracoid, and to restrict the term coracoid to the element thus left nameless, M r . Lydekker suggests the term ' metacoracoid' for the Cuvierian coracoid of Monotremes, and the ' coracoid epiphysis ' of the higher mammals which I have claimed as its homologue. I would no less gladly accept his proposals than he would m y own, but for the following very grave consideration. The observations of Goette and others leave no doubt that the coracoid and epicoracoid of the Mammal on the one hand, and the single so-called coracoid of the Amphibia, living Reptilia, and Birds, on the other, are derivatives of that 1 It is interesting to note that Bradypus tridactylus, in the adult of which the clavicle is par excellence attached to the coracoid, is the very mammal in the young of which Hoffmann has detected the primary continuity between the precoracoid and acromion. (Niederl. Arch. f. Zool. Bd. v. p. 37.) 2 Loc. cit. pp. 196, 197. 3 With the possible exception of the Ichthyosauria and Nothosauria, in accordance with Seeley's recent observations. M y friends in the Natural History Museum have accorded m e the privilege of examining Prof. Seeley's specimens, and I entirely agree that an unossified ventro-dorsal continuation of the Ichthyosaurian coracoid was present in the region in which he believes it to have been. It seems to me, however, that the notion that a separate (distinctly segmented) epicoracoid existed must remain in abeyance, until at least its impress shall have been discovered in the matrix. |
