150 PROF. OWEN ON NEW AND RARE CEPHALOPODA. 
The mandibular, radular, and salivary organs are almost in miniature what is shown 
in the same apparatus of the large Cephalopod next to be described, and justify the 
reference of the Hunterian specimen no. 508 to the following genus and species :— 
Genus ENOPLOTEUTHIS, d’Orb. ! 
Species EnopLorevtuis Cooxil, Ow. 
The beak (Pl. XXX. figs. 1, 2, 3) consists, as in all Cephalopods, of an upper (fig. 1) 
and a lower (fig. 3) mandible ; and, as in all the Dibranchiate kinds, the hardest part 
does not exceed the density of horn. In each mandible may be distinguished an 
anterior exposed, or “rostral” part (a bef), and a posterior concealed part (d g), which, 
as affording attachment to the biting-muscles, may be termed “ apophysial.” This is 
the part in which the corneous density degenerates into a kind of gristly flexible tissue. 
As in all Cephalopods, the lower mandible receives the upper when the beak is 
closed. 
The rostral part of the upper mandible (fig. 1) sends forward a long, somewhat 
slender, decurved, sharp-pointed “ uncus,” a, 11 lines (=23 millims.) in length at the 
lower border, as defined by the “ala.” This part, b, descends vertically with a feebly 
convex anterior border to apply itself to the inner surface of the corresponding part of 
the lower mandible (fig. 3, f). The upper border of the “ uncus” is continued backward, 
in a convex curve, 3 inches from the apex. The hind border, ¢, of the rostrum has an 
extent in a straight line of 22 inches; it describes a sigmoid curve concave forward in 
the upper three fourths, convex below, both curves feeble. The “apophysis,” d, d, is 
continued 31 inches behind the rostrum. Its upper part begins 9 lines (=20 millims.) 
below the hind and upper apex of the rostrum; the lower border quits the rostrum 
much nearer the lower apex of the ala,. Much of the interior border of the apophysis 
becomes free very near the hind border of the rostrum, ¢, leaving a long but shallow 
groove for the tendinous insertion of the supramandibular muscle; but a ridge-like 
extension continues the under or oral surface of the rostrum backwards, forming a horny 
roof of the fore part of the mouth, the extent of which is shown in the vertical section 
given in fig. 1, Pl. XXXI. The apophysial plate expands vertically as it retrogrades 
to its mid extent, Pl. XXX. fig. 1, d, d, where the vertical diameter is 2} inches; it 
then contracts, describing a sigmoid curve to the upper apex. The whole length, in a 
straight line, of the upper mandible is 4% inches. The extent of the hinder cartila- 
ginous border is from 2 to 3 lines, as indicated by the dotted outline in fig. 1. 
The lower mandible (ib. fig. 3) has a smaller apophysis and a shorter but deeper 
and rather less sharply pointed uncus, e (Pl. XXX. figs. 2&3). From the base of the 
uncus is continued a broad ala, f, overlapping the corresponding part, b, of the upper 
1 Histoire Naturelle des Céphalopodes Acctabuliféres, p. 336. 
