Preoperculum margine integro nec spinifero, disco arcto, inaequali, esquamoso, genam squamosam postice et infra cingens.  Operculum tridentatum:  Suboperculum crenatum; utrumque et interoperculum latiusculum squamis satis magnis tecta.  Dentes villiformes, minuti cum dente canino in media utroque latere maxillae inferioris et trans apicem utriusque maxillae dentibus quatuor (vel sex) fortioribus, altioribus, in serie exteriori ordinatis.  Dentes vomeris et palati acuti, stipati minuti.  Dentes pharyngei, acerosi inequales, acuti.

Membrana branchialis radiis sex sustentata, interoperculis liberis, accumbentibus tecta.

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,