Miscellaneous. 547 



more advanced specimen of Ornifhorhi/nchiis ; whilst the third was an 

 Echidna of about the same stage as the earlier of Professor W. N. 

 Parker's specimens. All the stages were more advanced than those 

 of Echidna lately investigated by Seydel. Wax-plate reconstructions 

 of the anterior snout region were exhibited, together with serial 

 photographs of the younger Ornithorhy nchv s. 



The following features are revealed and illustrated by the 

 models: — (1) The complete continuity of the nasal floor cartilage 

 and the extensive marginal cartilage of the upper lip, which in 

 the adult are separated by the premaxillae. (2) As a re.sult of this 

 continuity the premaxillae arise each as two entirely distinct bony 

 splints on the dorsal and ventral surfaces of the cartilaginous plate 

 aforesaid, (3) The great forwai'd expansion of the so-called rostral 

 cartilage of the Ornithorhynchus is seen to be due to the forward 

 growth of two bilateral alar expansions of the same cartilage, which 

 tend to meet in front after enclosing a deep notch corresponding to 

 the hiatus described by Broom in the rostral cartilage of the adult. 

 (4) The ventral lamelhe of the premaxilla? are provided with true 

 palatine processes directed backwards paramesially. In the older of 

 the two stages of Ornithorhiinchus there exists, quite independently 

 of the palatine process, and separated from it by a considerable 

 interval, a separate ossification for the dumbbell-shaped bone, which 

 is thus proved to be a perfectly distinct element — a true anterior 

 vomer. (5) Anteriorly, the ventral premaxillary sjilints turn up 

 dorsally in front of the anterior extremity of the snout in both 

 Ornithurhii nchus specimens, in the form of rather attenuated 

 trabeculsB, lodged in the notch between the alar expansions of the 

 rostral cartilage. Above this plane they fuse and are continued 

 dorsall}" into a remarkable osseous mass which forms a definite 

 skeletal foundation for the caruncle, and may therefore be named 

 the OS caruuculae. This is at its maximum development in the 

 younger stage of Ornithorhynchus, and is undergoing resorption in 

 the older ; whilst in the Echidna model it is only represented by a 

 small nodule of bone which has lost all connexion with the pre- 

 maxillae. From Seydel's figures of earlier stages it is evident that 

 the Echidna condition is originally identical with that of Ornitho- 

 rhy)ichus, though it would appear to exist in a less exaggerated 

 form. (6) The cartilaginous septum of both Monotremes exhibits 

 an oval " internasal fenestra " immediately behind its anterior 

 termination at the prerostral notch. A similar fenestra, according 

 to W. K. Parker, is "a common feature in low Eutheria." — Linn. 

 Soc. of New South Wales, Abstract of Proceedings, March 28, 1900, 

 pp. iii-iv. 



