34 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
One specimen 2 inches long was taken by the Challenger on July 26, 1875, in latitude 23° 3' N., 
longitude 156° 6' W., a few degrees north of Honolulu. (Gunther.) Other specimens were secured 
by the Albatross in 1902. The species is supposed to differ from other lancelets in living toward the 
surface in deep water instead of burying itself in the sand at small depths. There is considerable doubt 
as to this, however, and as to some of the characters ascribed to the species. 
Branchiostoma pelagicum Gunther, Pelagic Fishes, Challenger Rept., Zoology, XXXI, part II, 43, pi. VI, tig. B, 1888 
(1889), lat. 23 0 3 ' N., long. 156 ° 6 ' W. 
Amphioxidespdagirus, Gill, Am. Nat., vol. xxix. May, 1895, 458 (after Gunther). 
Glass II. PISCES. The Fishes. 
The Pisces, or fishes, may be defined as cold-blooded vertebrates adapted for life in the water, 
breathing bv means of gills which are attached to bony or cartilaginous gill-arches, the gills persistent 
throughout life; having the skull well developed and provided with a lower jaw; the limbs present 
and developed as fins, rarely wanting through atrophy; shoulder-girdle present, furcula-shaped, 
curved forward below, rarely obsolete or represented by cartilage; pelvic bones present; exoskeleton 
developed as scales, bony plates, or horny appendages, or sometimes entirely wanting; and with the 
median line of the body provided with one or more tins composed of cartilaginous rays connected by 
membrane, the fins rarely atrophied. 
SUBCLASSES OF PISCES REPRESENTED IN HAWAIIAN WATERS. 
a. Skull without system of membrane bones (opercles, etc.). 
b. Suspensorium of the mandible present; gills not free, being attached by the outer margin to the skin; eggs few and 
large, impregnated and sometimes developed internally, covered with a thick leathery skin when developed 
externally; embryo with deciduous external gills; no membrane bones about the head; upper jaw formed of 
palatine and pterygoid elements without maxillary or premaxillary; skeleton cartilaginous; skull without 
sutures; tail heterocereal; ventral tins abdominal; male with large intromittent organs or claskers attached to 
the ventral fins, these complex in structure in existing species; shoulder-girdle not attached to the skull; skin 
naked or covered with small rough scales, spines, or bony bucklers; no air-bladder; arterial bulb with 3 series of 
valves; optic nerves with a chiasma; cerebral hemispheres united; gill-openings slit-like, 5 to 7 in number; jaw 
distinct from the skull, joined to it by suspensory bones; teeth distinct; (Sharks and Skates). Selachii, p. : 4 
bb. Suspensorium of the mandible wanting; no maxillary arch; ventral tins with elaspers; gill-opening single, leading 
to 4 gill-slits; jaws coalescent with the skull; teeth united in the form of bony plates; l Chvmscras). 
Holocephali, p. 51. 
aa. Skull with a well-developed system of membrane bones (opercles, suborbital ring, etc.); gills free, attached to the 
gill-arches by their bases only; gill-opening single on each side; eggs comparatively small and numerous; no 
elaspers; a maxillary arch; cerebral hemispheres not united; (True Fishes). Tcleostomi, p. 52. 
Si_it>ela.ss SELACHII. — The Sharks ciiiul Skates. 
This group includes among recent fishes, the sharks and rays, marine fishes, mostly of large size, 
abounding in all seas. 
ORDERS OF SELACHII REPRESENTED IN HAWAIIAN WATERS. 
a. Gill-openings 5; vertebral column well segmented, each segment forming a neural arch and one centrum. 
It. Vertebne each with the internal calcareous lamellae radiating from the central ring; anal tin present. 
Asterospondyli, B, p. 34. 
bb. Vertebrae with the internal calcareous lamellae not radiating, but arranged in one or more concentric circles or series 
around the central ring; no anal tin; palato-quadrate arch not articulated to the skull. 
c. Gill-openings lateral; dorsal fins 2 . Tectospondyli, C, p. 44. 
cc. Gilkopenings ventral; dorsal fins small and posterior, or wanting; body and pectorai fins forming a depressed disk. 
Batoidei, D, p. 4G. 
Order B. ASTEROSPON D Y LI. 
The essential character of this order is the structure of the vertebrae. The calcareous lamella- 
within each vertebra radiate from the central ring. The group contains the great body of living 
sharks, including all of those with 5 gill-openings, 2 dorsals, and an anal tin. 
Suborder GALEI.—THE TRUE SHARKS. 
Asterospondylous sharks with the palato-quadrate apparatus not articulated with the skull; gill- 
openings always 5 and always lateral; dorsal fins 2, well developed, each without spines. This suborder 
contains most of the living sharks. 
