1870. | HANCOCK AND HOWSE—DORYPTERUS HOFFMANNI. 631 
the plates are divided by a lanceolate space. The tapering distal or 
outer extremities of the lateral plates are united each to a stoutish 
rod (7), which at the point of union is cylindrical and somewhat 
enlarged. These are slightly arched backwards and inclined consider- 
ably in the same direction; their outer extremities are a little 
widened, flattened, and grooved longitudinally ; and, suddenly con- 
tracting, they turn forwards, and each becomes joined to the inner 
pointed extremity of a sigmoidal ridge-like plate (7), which rises boldly 
up, and which, inclining much forward, terminates in a recurved 
sharp point a little within the general margin of the fish. The sig- 
moidal ridges gradually widen in the centre, where there is a longi- 
tudinal groove ; and they, as well as the rods, are divided trom each 
other by a considerable space. Such is the general appearance of these 
sigmoidal ridges or plates; but on closer examination the ridges are 
found to be formed of the turned-up edges of wide flat sigmoidal 
plates( 7’), which extend from ridge to ridge. 
Such is the description of the transverse series of plates and rods 
of the posterior half of the body, numbering sixteen or seventeen 
corresponding to the caudal vertebrae, to which the lozenge-shaped 
areas and lateral plates have a strong resemblance. On the anterior 
half the dorsal members of the transverse plates and rods are some- 
what modified. The central lozenge-shaped plates bearing the 
ridges and the elongated lateral plates are continued to the occiput 
unaltered in character, or only slightly changed in form. Below, or 
towards the ventral margin, the sigmoidal ridges or plates seem to 
be replaced by a series of seven large thoracic or ventral plates (m), 
which are arranged along the margin of the body, those of the two 
sides meeting on the median line, where doubtless they formed a 
sharp edge. They are 2 inch long, and about 4 inch wide. 
They appear to imbricate forwards, and are of an irregular ovate 
form, with the posterior margin thin and somewhat flattened, and 
the anterior or overlapping margin thickened, grooved, and a little 
shouldered above. We say appear to imbricate forwards ; but in the 
most perfect specimens there are indications that they are really im- 
bricated backwards, the groove of the anterior margin receiving the 
thin posterior border of the preceding plate; and the appearance to 
the contrary seems to be owing to dislocation. Both extremities of 
the plates are drawn out, the lower one being considerably pro- 
longed, pointed, and directed backwards. The upper extremities 
are directed upwards and forwards, and are produced into widish 
columns (n) (the ribbon-shaped organ of Germar), the two or three 
anterior of which, increasing in length backwards, terminate imme- 
diately behind the clavicle. The posterior ones pass upwards, and are 
united to the outer extremities of the lower lateral plates near the 
occiput. These columns, which are divided by narrow spaces, pre- 
sent a very peculiar appearance. Hach of them is composed of nume- 
rous, narrow, much elongated plates or rods, with pointed extremi- 
ties, which, overlapping each other considerably, give to the whole a 
sort of twisted look. They are probably, however, in a disturbed 
state. About seven of the lower lateral plates next the occiput are 
VOL. XXVI.—PART I. 3A 
