OCR Text |
Show 1899.] FROM THE GOLD COAST. 721 head without snout or as the spine of the pectoral, very slightly serrated along its posterior, and nearly smooth along its anterior edge. Anal fin not reaching the caudal, when laid backward, with 11 or 12 rays, 7 or 8 of which are branched. Caudal fin deeply cleft, with the upper lobe as long as the head. Upper parts greyish brown, lower silvery. Three specimens from the River Prah, 91 and 139 millim. long. This species represents in the Gaboon rivers the Nilotic Chrys-ichthgs macrops, to which it is closely allied. In that species, however, the anterior dorsal ray is greatly prolonged, even in specimens which exceed the Prah fishes only slightly in length. CHRYSICHTHYS BUTTIKOFERI Steind. (Plates XLI. & X.LII. fig. A.) Chrysichthys buttikoferi. Steindachner, Notes Leyden Mus. xvi. p. 60 (1891). The examination of a small number of: (chiefly young) specimens of Chrysichthys from various localities in the Gaboon country has been attended with much difficulty and uncertainty. A part of them seemed to be identical with, or closely allied to, Ch. buttikoferi (Steindachner). Although they show certain slight differences in the number of anal rays, extent of the tooth-patches on the palate, form and comparative length of the snout, size of the eye, and length of the dorsal and caudal rays, Steindachner's description applied more or less perfectly to all. However, the series of specimens of any species from the same locality is still so incomplete that we are much in the dark as to individual variations, the changes these fishes undergo with age, or as to any secondary sexual characters. Some years ago I should not have hesitated to refer all these specimens to the same species Ch. biittikoferi, and I am not by any means certain that this will not prove to be the proper course to pursue, when sufficient materials are brought together ; but since more recent investigations of the West African Fauna have shown the wide distribution and great specific development of this genus, I am induced, after long hesitation, to distinguish among the forms allied to Ch. biittikoferi several under distinct names. The question, then, arises for which of the forms, distinguished here, the name given by Steindachner should be retained. Steindachner's type came from Liberia, is a unicum, and young, being 20^ centim. long. I am indebted to Dr. Jentink for a sketch of "this type as well as of its dentition. Unfortunately the specimen presents those elements of uncertainty which render the study of these fishes so difficult. As will be seen from the accompanying sketch, the two patches of larger vomerine teeth are connected' with each other by, and are in fact only a portion of, a larger horseshoe-shaped band of minute rudimentary vomerine teeth extending backward on the palatine bones. In the River Prah specimens referred by me to Ch. biittikoferi only the two patches of larger teeth are visible, but none of the rudimentary ones. |