Fig. 334.—Slippery-dick or Doncella, Halichœres bivittatus (Bloch), a fish of the coral reefs. Key West. Family Labridæ.
Very many species of both Scarus and Pseudoscarus, green, blue, red-brown, or variegated, abound about the coral reefs of Polynesia. About twenty-five species occur in Samoa. Pseudoscarus latax and P. ultramarinus being large and showy species, chiefly blue. Pseudoscarus prasiognathus is deep red with the jaws bright blue.
Fossil species referred to Scarus but belonging rather to Sparisoma are found in the later Tertiary. The genera Phyllodus, Egertonia, and Paraphyllodus of the Eocene perhaps form a transition from Labridæ to Scaridæ. In Paraphyllodus medius the three median teeth of the lower pharyngeals are greatly widened, extending across the surface of the bone.
CHAPTER XXIII
THE SQUAMIPINNES
Fig. 335.—Monodactylus argenteus (Linnæus). From Apia, Samoa. Family Scorpididæ.
The Squamipinnes.—Very closely allied to the Percomorphi is the great group called Squamipinnes (squama, scale; pinna, fin) by Cuvier and Epelasmia by Cope. With a general agreement with the Percomorphi, it is distinguished by the more or less complete soldering of the post-temporal with the cranium. In the more specialized forms we find also a soldering of the elements of the upper jaw, and a progressive reduction in the size of the gill-opening. The ventral fin retains its thoracic insertion, and, as in the perch mackerel-like forms, it has one spine and five rays, never any more. The ventral fins are occasionally lost in the adult, as in the Stromateidæ, or they may lose part of their rays. The name Squamipinnes refers to the scaly fins, the typical species having the soft rays of dorsal, anal, and caudal, and sometimes of other fins densely covered with small scales. In various aberrant forms these scales are absent. The name Epelasmia (ἔπι, above; ἐλάσμος, plate) refers to the thin upper pharyngeals characteristic of certain forms. The transition from this group to the Sclerodermi is very clear and very gradual. The Squamipinnes, Sclerodermi, Ostracodermi, and Gymnodontes form a continuous degenerating series. On the other hand the less specialized Squamipinnes approach very closely to forms already considered. The Antigoniidæ are of uncertain affinities, possibly derived from such forms as Histiopteridæ, while Platax show considerable resemblance to scaly-finned fishes like the Kyphosidæ and Stromateidæ. The Scorpididæ seem intermediate between Stromateidæ and Platacidæ. In such offshoots from Scombroidei or Percoidei the group doubtless had its origin.
We may begin the series with some forms which are of doubtful affinity and more or less intermediate between the Squamipinnes and the more primitive Percomorphi.