BRITISH FOSSILS. \'j 



suspecting that it belonged to some of the species which have pro- 

 ostraca like that of Belemnites Bruguierianus. 



But I am by no means satisfied of the justice of Voltz's assumption, 

 which D'Orbigny and others adopt, that the conothecal lines must 

 indicate the form of the pro-ostracum, since the hitter may readily 

 have been modified by the deposition of shelly matter upon its exterior, 

 after its first formation. 



2. The guard of the typical specimen of Belemnites elonyatus, now 

 in the British Museum, is covered by a superficial, smooth, thin, 

 whitish, cuticular pellicle ; and a better developed cuticle of the same 

 kind has been brought under my notice by Mr. Day in specimens from 

 the Upper Lias. A small example of the guard of apparently the 

 same species (PL I., figs. 3, 3a, 3b), pointed out to me by Mr.* Day, 

 exhibits a much more developed cuticle. This is thrown into fine 

 longitudinal wrinkles in its upper part, but, inferiorly, the wrinkles 

 pass into minute ridges and tubercles. Both these and the wrinkles 

 are larger, and extend farther up, on the dorsal than on the ventral, 

 aspect of die guard. 



I? the existence of this cuticular pellicle an indication of the com- 

 pletion of the growth of the Belemnite '! 



3. A splendid specimen in the collection of Mr. Norris (Plate II., 

 figs. 1 and la) shows very clearly the association of a phragmocone with 

 a nacreous pro-ostracum and a large ink-bag. On the one face (fig. 1) 

 this fossil exhibits the dorsal part of the pro-ostracum and its con- 

 tinuation into the guard, while, on the other face (fig. la) the huge 

 ink-bag is displayed. The saddle-shaped, highly iridescent, region of 

 the dorsal part of the pro-ostracum (a) terminates in well defined 

 margins, both laterally and in front, the portion of the pro-ostracum 

 with which it was continuous, at the sides, having broken away from 

 this central region. On the left side, however, the lamellar continua- 

 tion of the pro-ostracum towards the ventral surface (b) is well shown ; 

 and, like the dorsal portion, it is highly iridescent. When subjected 

 to an oblique light, the pro-ostracum exhibits a shallow medio-dorsal 

 longitudinal groove and indistinct lines of growth, which are convex 

 upwards. The surface which continues the direction of the iridescent 

 part of the pro-ostracum upwards (c) has a granular pitted surface ; 

 but I am doubtful whether this appearance is due to the structure of 

 the pen in this region, or to the manner in which fossilization has 

 taken place. 



The ink-bag is flask-like, 8 inches long, and If inches wide at 

 widest 



4. In Mr. Day's collection, there is a specimen (No. 9) from the 

 Ammonites obtusus zone, consisting of the upper part of the phrag- 

 mocone, with almost the whole of the pro-ostracum, and the remains of 

 many hooks in place. 



A length of about 2| inches of the phragmocone is preserved ; its 

 upper end is 2-^ inches wide, its lower end somewhat more than 1 inch, 

 but both ends are greatly crushed. Nacreous shelly substance coats 

 the exterior of the upper part of the phragmocone, and extends upwards 

 over more than the lower half of the pro-ostracum, which has an oval 

 form, and is nearly 10 inches long by 3 inches wide. 



The upper four or five inches of the middle portion of the pro-ostra- 

 1 cum is formed of a thin plate of shelly matter, which is not iridescent, 

 and beneath which there is no iridescent nacre. In the lower part of 

 the pen the external non-iridescent substance has a subjacent, beautifully 

 iridescent layer. In this, a> in other cases, the nacre is bounded by "a 

 well-defined upper contoiT. which in this instance is con . 



