64 Prof. J. Van der Hoeven on the Anatomy 



filaments, just like a border of fringe. At the commissure of 

 the large tentaculiferous slii)s are found on the inside many- 

 furrows which are parallel to its excised anterior margin ; whilst 

 at the side and further back there are small cavities, from which 

 the part obtains a retiform aspect. A continuation of the skin, 

 at about 1 centimeter behind the excised margin, mounts up- 

 wards as a thin investment, to cover the tongue-bone, so named 

 by Owen, and the entire muscular apparatus of the jaws, and 

 passes into the skin arising from the dorsal surface, or rather 

 forms a whole with it. Downwards, however, this membrane 

 forms still another duplicature, a blind longitudinal sac, which 

 invests a composite organ. From the ti'ansverse fissure above 

 the duplicature, this organ comes partly into view by its superior 

 margin. It is about 14 mm. broad and 18 mm. long, convexly 

 oval on its upper surface, flat on its inferior surface, and lies like 

 a little cushion below and behind the tongue-bone, and next the 

 under surface of the commencement of the oesophagus. On 

 opening the fold of skin that encloses it, this organ is found to 

 consist of two lateral parts, bean-shaped, and turned towards each 

 other at the foie-part with a convex margin. These two margins 

 are divided by seven or more incisures* of 2 to 3 mm. in depth, 

 into flat quadrangular slips that become narrower inwards. If the 

 two lateral parts be separated from each other by a longitudinal 

 section, then in each of them about fourteen other very thin 

 laminae are seen running obliquely towards the inner margin and 

 downwards. The most external of these lamina lies next a 

 sinuous, smooth part, which becomes broader downwards. On the 

 outside of this part is a small cavity within the very thick outer 

 wall, which is formed by transverse loose fibres. 



Let us now compare this disposition with what occurs in 

 female individuals of Nautilus. Here there are on each side two 

 lobes, which are divided into digitiform slips {labial processes, 

 Owen) . The uppermost pair is broader, and usually or almost 

 always bears twelve tentaclest- The fold of skin which unites 

 these lobes at the under side with the most external large tenta- 

 culiferous shps is covered by a number of fine membranous 

 leaflets, which are distinguished into two groups. The under- 

 most pair lies wit kin the circle of the uppermost, and imme- 

 diately towards the membranous mass which surrounds the jaws ; 

 they consist of a styliform part, which passes into a broader 

 hand-shaped part forwards, and mounts at the side towards the 

 membranous oral mass. Here I found sixteen tentacles on the 



* In the specimen investigated by me in 1847, there were ten or eleven 

 of these tetragonal slips. Trans, of Zool. Soc. iv. 1. p. 27. pi. 8. fig. 9. 



t Here Owen and W. Vrolik found twelve tenfo.cula, with which my 

 observations constantly agreed ; Valenciennes found thirteen. 



