Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/865

 smooth, without stride or granulations ; but their appearance is not very distinct. The hind border of the operculum or gill-plate is narrow ; near to it is placed the left pectoral fin, which has probably been pushed so high up by pressure from without. One recognizes only the impressions of a few rays : below, on the margin near the anal, the rays of a small fin are shown, which appear to have belonged to the ventral ; for although, until now, on the specimens of the genus Platysomus which have been examined by Agassiz, Germar, and others ventral fins have not been seen, yet I have found them on two examples of P. Fuldai (= Platysomus macrurus, Ag.).

" The dorsal fin is somewhat large ; the commencement of it is near the head, in the central part of the back. The anal stands opposite to it, and is nearly of the same form and size, but is situated nearer to the mouth than to the tail ; for it reaches nearly to the head. The rays of both fins run to the tail, and are very fine. On the example before us, fragments only of the rays of the continuation of the dorsal could be seen.

" The pedicle of the tail is remarkably narrow, only about a line broad; the deep-forked fin is proportionally very large. Of both lobes the extremity is wanting ; but it seems that the upper lobe was not much longer than the lower, which is a little broader. " There is, as mentioned before, no trace of the scales."

In Minister's figure of P. Althausii, the posterior part of the body, allowing for the slightly different state of preservation, much resembles ours. The form of the abdominal cavity, bounded in front by the " ribbon-shaped process," and posteriorly by the abdominal rod, is identical. The position of the pectoral fin is also the same, though thought by Munster to have been disturbed and pushed upwards out of its true position. The prolongation of the dorsal fin is destroyed, as in most of our specimens ; and the bones of the head are much displaced, and moved downwards and backwards towards the ventral cavity ; but these bones are said to be smooth and without striae or granulations — a character which at once distinguishes this fish from Platysomus, in which the bones of the head are always more or less ornamented with granulations or striae.

In Munster's example the anal fin is finely preserved, and shows very distinctly its continuation to the tail ; but by displacement and pressure of the bones of the head downwards, the ventral fins, which Munster saw, but could not describe rightly on account of the disturbed state of his specimen, have been pushed backwards, and brought nearly into contact with the anal fin ; and thus one of the striking peculiarities of Dorypterus (the thoracic or jugular position of the ventrals) remained till now unobserved. It will, we think, be admitted by every one who carefully collates Munster's figure and description of P. Althausii with those of Germar's Dorypterus Hoffmanni, that they are perfectly identical ; and we adopt the latter name for the species, as it has a slight precedence in order of description, and was, besides, more strongly characterized than the former.

The German specimens of Dorypterus were obtained from the