256 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 
Order M.-ISOSPONDYLI. 
[The Isospondylous Fishes.) 
Parietals present. S.ymplectic present. Xo interclavicles. A i)riecor- 
acoid arch. Anterior vertebrae simple. Xo auditory ossicles. Pliaryn- 
genl bones simple above and below, the lower not falciform. Gills 4, a 
slit behind the fourth. A very large group, presenting many modifica- 
tions of structure, equal; vertebra.) 
{Physostomi Giiutlier, part.) 
ANALYSIS OF FAMILIES OF ISOSPONDYLI. 
* Tail (lijthycercal. 
a. Lateral margins of upper jaw formed by the maxillaries. 
b. Adipose fin none : no phosphorescent spots; body usually scaly ; head naked; 
throat without barbel. 
c. Lateral line present. 
d. Gnlar plate none. 
e. Air-bladder none ; dorsal posterior, opposite anal and similar to it ; mouth 
small, with small, pointed teeth; deep-sea fishes. 
ALEPocEPiiALiDa:, 33. 
ee. Air-bladder present ; dorsal in front of anal. 
/. Mouth small, horizontal ; posterior part of tongue and the roof of the 
mouth covered with coarse, paved teeth. .. ALBULim-E, 34. 
ff. Mouth larger, obliixue; teeth all iiointed; those on the tongue large. 
Hyoi)Ontid.e, 35. 
dd. Gular plate present ; mouth large; teeth all iioiuted Elopid.e, 36. 
cc. Lateral line obsolete. 
y. Mouth terminal, large ; maxillaiy in three jiarts, mostly broad. 
Clupeid^, 37. 
yg. Month small, inferior ; maxillary short and narrow ; not in tlu’ee 
jiarts D 0 ROSOMATID.E, 38. 
yyy. Mouth very large, subinferior; maxillary very narrow, xiioduced 
backward Engraulidid^, 3'J. 
bb. Adijiose tin present (rarely absent, and the liody with j>hos|>horescent sxmts). 
h. Throat with a long barbel ; scales very small or wanting ; mouth 
large Stomiatipa-:, 45. 
hh. Throat wiMiout barhel. 
/. Sides with i)hosi>horesceut sx)ots; oviducts xiresent; deex)-sea 
fishes. 
j. P.seudobrauchiiB none; body scaly Chauliodontid/E, 44. 
jj. I’seudobranchia} body naked. .Sterxoptyciiiu.e, 43. 
a. Si<les without xdiosphorescent sjiots; oviducts none. 
Salmon I n.E, 46. 
aa. Lateral margins of ujuier jaw, like the anterior margin, formed by the jiremax- 
illaries ; adipose fin usually xireseiit. 
k. Premaxi llaries short, with villiform teeth; mouth small; 
bones of head cavernous ; scales ctenoid. .PERCOPSiDiE, 47. 
kk. Premaxillaries elongate; mouth large; bones of head not 
cavernous; scales mostly cycloid. 
I. Dorsal short, nearly median ; body scaly.. S copelid.e, 12. 
II. Dorsal short, jiosterior; body scaly .. Paralepididze, 41. 
III. Dorsal occuiiying nearly the whole length of the back; 
body naked Alepioosaurid.e, 40. 
