Squamae satis magnae, nitidae ciliatae. Linea lateralis antice abrupte ascendens, dein dorso parallela et approximata, postice diffracta infraque per mediam caudam cursum resumens.
Pinnae magnae esquamosae. Pinna dorsi anique radiis tribus, spinosis, ceteris articulatis. Pinnae ventrales sub pectorales offixae, propter tenuitatem ventris invicem approximatae.
The strong resemblance which the subject of this article bears to the Pseudochromis olivaceus of Dr. Ruppell (Neue Worlbethiere, page 8, taf. 2, figure 3) induced me at first sight to refer it to the same genus, but on examination I found that very material alterations would require to be made in the generic characters assigned to Pseudochromis,* to enable them to apply to our fish.
(*Footnote. M. Swainson, considering this name as very objectionable, has proposed Labristoma instead. Both names are founded on the resemblance which the fish bears to another genus, in whole or in part, and the objection which has been made to the one is equally valid against the other.)
The above character has therefore been drawn up, and ichthyologists may consider Assiculus, either as a proper generic form, or as merely a subgenus or subdivision of Pseudochromis, with an extended character, according to their different views of arrangement. The last named genus, as described and restricted by Dr. Ruppell, from whom all our knowledge of it is derived, has the jaw teeth disposed in a single row, and the minute palatine teeth of a sphaeroidal form. The operculum has its angle prolonged, and is not toothed, nor is the suboperculum crenated; and a considerable number of the rays of the dorsal fin, succeeding to the three spinous ones, are simple but flexible, the posterior ones only being articulated and divided in the usual manner. Linnaeus has briefly characterized two fish (Labrus ferrugineus, Bl. Schn. page 251, and Labrus marginalis, Id. page 263) which most probably belong, either to Pseudochromis or Assiculus, and which are to be placed, M. Valenciennes thinks, near Malacanthus, among the Labridae. Now, this family, according to M. Agassiz, is essentially cycloid in the structure of its scales, although there is a slight departure from the rigid characters of the order in the serrated preopercular of Crenilabrus, Ctenolabrus, and some others, and in the spine bearing operculum of Malacanthus. The latter genus is, moreover, described by M. Agassiz as possessing scales with toothed edges, and rough to the touch when the finger is drawn forwards. It has the simple intestinal canal without caeca, which is proper to the Labridae. The intestine of Pseudochromis is similarly formed, the stomach being continuous with the rest of the alimentary canal, and not distinguished by any cul de sac. Having but one specimen of Assiculus for examination, I have not been able to submit it to dissection to see whether the structure of its intestines be the same or not, but both it and Pseudochromis differ very widely from the labroid type in their scales, possessing the peculiar firm, shining, strongly ciliated structure, which we observe in Glyphisodon and its allies, and in the lateral line being interrupted in a precisely similar manner. Chromis and Plesiops have already been removed by M. Valenciennes from the Labridae to the Glyphisodontidae, and it is with them that we feel inclined to range Assiculus and Pseudochromis, notwithstanding the discrepancies in the form of the intestinal canal. We can, however, trace a gradation in the variation of form. The normal number of caeca in the Glyphysodontidae is three. In Chromis there are generally two small ones, while the Bolti of the Nile, or the Chromis niloticus of Cuvier, has no pyloric caecum, but a large cul de sac to the stomach. Malacanthus is widely separated from the Glyphisodontidae by its continuous lateral line. Since these remarks were written I have seen Muller's paper, entitled, Beitrage zur Kentniss der naturlichen Familien der Fische, in which the Chromidae are indicated as a distinct family from the Glyphisodontidae, which latter he names Labroidei stenoidei; and Pseudochromis, it is stated, belongs to neither of these families, because it has twofold pharyngeals with a division between them. Dr. Muller promises a separate article on Pseudochromis, which I have not yet seen.
Assiculus punctatus.
RADII. BR. 6; D. 3 : 23; A. 3 : 12; C. 21; P. 18: V. 1, 5.
FISHES. PLATE 2. Figures 1, 2, 3, 4, and 5.