91 



in diameter at tlieir base, and projecting to the distance of a line 

 beyond the general surface of the niantle. 



The viscera occupy but a small portion of the cavity of the mantie, 

 in which they are placed far backwards, the hranchice themselves not 

 extending forwards beyond the niiddle of the sac. The liver is di- 

 vided, as in Nautilus, into four principai lobes, vvhich are quite se- 

 parate from each other; but the lobules vvhich corapose these lobes 

 are not, as in the Testaceous Cephalopod, detached from each other. 

 The branchial arteries are surrounded, before entering the auricles, 

 by a spherical cluster of vesicles, likę those which open into these 

 vessels in Nautilus ; but the auricles are not, as in Nautilus, wanting: 

 they are, however, destitute of those singular appendices usually 

 found attached to these muscular sacs in the Naked Cephalopods. 

 The hranchice are single on each side, and are proportionally the 

 smallest which Dr. Grant has yet met with. The systemic ventricle 

 is very muscular, aud of a lengthened fusiform shape : it has an 

 aortai trunk at each end. On the large dorsal or descending aorta 

 there is, as in Nautilus, a distinct buTbous enlargement, probably 

 the coinmeiicemeiit of a bulbus arteriosus. 



In Setnola, in addition to the usual dorsal lamina which is thin 

 and short, there exist, external to the mantie and supporting the 

 fins, two firm crescentic cartilaginous platės, likę scapulce, playing 

 freely on the outer surface of the mantie, and furnished with an outer 

 and an inner layer of museles, passing in the form of minute white 

 Jasciculi, from the middle of the dorsal part of the mantie : by this 

 structure, great extent and effect are given to the motions of these 

 povverful dorsal arms, which have thus a singular resemblance in 

 their mode of attachment to the anterior extremilies of Vertebrata. 



The cavity of the mantie is comparatively small, and its vvhole 

 extent is occupied by the viscera, which are largely developed, par- 

 ticularly the digestive organs, the ink gland, and the two glands of 

 the oviducts. The ink gland is remarkable for its form as well asits 

 magnitude. It consists of three longitudinal lobes placed trans- 

 versely, and extending more in that direction than lengthvvise. The 

 two lateral lobes are kidney-shaped ; the third or middle lobe is 

 smaller, and from its upper part the duct arises. 



The Secretary read a communication from M. GeofFroy-Saint- 

 Hilaire, entitled " New Observations on the Nature of the Abdo- 

 minal Glands of Ornithorhynchus ," in which the author statės it to 

 be his purpose to reply to the observations of M r. Owen on that 

 subject, contained in the Proceedings of the Society, unįer date of 

 the 12th of March in the present year (page30). 



" The question no longer regards merely the simple fact, whether, 

 decidedly and absolutely, the Monotremata are viviparous, or ovipa- 

 rous ; whether we should reason upon them according to the rules 

 oi'the past, and apply to them the entire character of /V/a>«?na//a ; or 

 whether we are not compelled to see in them sufficient anomalies to 

 embrace them in views of progress. 



" Let us State the case more precisely. There is but one single 



