i 



Miscellaneous. ,0 J 7 



more advanced specimen of Omithorhynchus ; whilst the third was an 

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

 I'iirker's siRcimens, All the stages were more advanced than those 

 of Echidna lately investigated by Seydel. Wax-plate reconstructions 

 of the anterior snciut region were exhibited, together with serial 

 photographs of the younger Ornithorhijnchus. 



The following features are revealed and illustrated by the 



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



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



the adult are separated by the preniaxillie. ('2) As a result of this 



continuity the j)reinaxilkt' arise each as two oritiiely distinct bony 



splints on the dorsal and ventral surfaces of the cartilugiiious phite 



aforesaid. (3) The great forward expansion of the so-ealled rostral 



cartilage of the Ornithurhijnchus is seen to bo 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 Eroom in the rostral cartilage of the adult. 



(4) The ventral lamelhc of the premaxilhv are provided with true 



I>alatine processes directed backwards paramesially. In the older of 



the two stages of Orniihorhijnchus 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 splints turn up 



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



(Jrnith<>rh>inchns specimens, in the form of rather attenuated 



trabecula>, lodged in the notch between the alar expansions of the 



rostral cartilage. Above this plane they fuse and are continued 



dorsally into a remarkable osseous mass which forms a definite 



skeletal foundation for the caruncle, and may therefore be named 



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



younger stage of Oniithorhi/iichus, 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- 



rhi/xchux, though it would appear to exist in a less exaggerated 



form. ((')) 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. 



