130 DEVONIAN FAUNA. 



about 1 : 4. Surface bearing distant transverse fine angular rings, situated 

 1 mm. or 2 mm. apart, gently arcMng as they cross the shell, and numbering 

 three upon each chamber. Interspaces between the rings gently concave, marked 

 with numerous fine parallel microscopical striae, which are frequently obliterated. 

 Colour black. 



Size. — None of the specimens known are sufficiently perfect to give any idea of 

 its proportions. One in the Battersby Collection is 4^ inches high by about ^ inch 

 in diameter. The shell is stated by the quarry-men sometimes to reach the length 

 of 7 or 8 inches. The largest specimen I know is about 23 mm, in diameter. 



Localities. — This Cephalopod appears to be not uncommon at Lummaton ; I 

 have obtained several small specimens from the shelly bed at the top of the 

 quarry, and specimens of a large size are found by the workmen in the massive 

 rock. I have seven or eight fragmentary specimens. There is a good specimen 

 in Mr. Lee's Collection, and a fine specimen in the Battersby Collection in the 

 Torquay Museum, which is in a sandy matrix, but may perhaps have come from 

 the same place. Mr. Vicary has five specimens from Wolborough, and there is 

 another in the Godwin- Austen Collection in the Museum of Practical Geology 

 from the same locality. A specimen in the British Museum, which has been 

 labelled by Mr. Foord " Orthoceras cf. Dannenhergi" is stated to come from 

 Torquay. 



BemarJcs. — This is an interesting and characteristic species. The test appears to 

 be very thin, and it is remarkable for the frequency with which it retains a blackish 

 colour. This colour is, of course, no criterion of its original tint, but doubtless 

 is indicative of some peculiarity, as at least at Lummaton it is only observable in 

 two or three other species of fossils, especially in Gapuhis. The surface markings 

 seem always to retain very much the same character ; the ribs becoming only 

 slightly more distant as they approach the upper portion. It is, however, curious 

 to observe how little their width varies in different-sized shells. Thus in a 

 specimen 23 mm. wide the rings are distant 2 mm., while in one only 5 m. wide 

 they are distant 1.2 mm. A comparison of numerous specimens leads me to 

 regard this as of little importance, and indeed a similar variation is apparent in 

 other species, as in 0. tublcinella. Unfortunately, the septa can very rarely be seen, 

 and therefore the relation they bear to the ribs either in number or in curvature 

 cannot be positively asserted. In the small specimen, however, in the Museum of 

 Practical Geology their relation, as well as the position of the siphuncle, is clearly 

 shown, and there it is seen that the rings are three times as numerous as the septa, 

 and agree with them in outline. There appears to be some amount of variation 

 in the arching of these ribs, as well as in the tapering of the shell. It is also 

 to be noted that in Mr. Vicary's large specimen, which probably includes the 



