200 MR. C. TATE REGAN ON THE 
in the young, whilst the fins have a few cross-bars, which later on break up into spots, 
and these spots, like those on the head and body, seem to continually increase in 
number with increased size of the fish. 
Measurements. 
In descriptions of species the total length means the distance from the tip of the 
snout to the base of the caudal fin; but where the total length (in millimetres) of the 
largest specimen described is given, the length of the middle rays of the caudal fin is 
included. In the armoured forms the length of the head is measured to the posterior 
margin of the temporal plate, but in the naked-bodied Argiine to the edge of the bony 
operculum. In some cases it has been found useful to indicate the size of the mouth 
by giving the proportion of the length of the mandibular ramus—v. e. of that box-like 
tooth-bearing portion of the mandible which borders the mouth—to the interorbital 
width. In counting the scutes, that one which is posterior to the clavicle is reckoned 
as the first, whilst the movable plates covering the bases of the caudal rays are not 
included. The length of the base of the dorsal fin is measured from the base of the 
first developed ray to the base of the last, the membrane behind the last ray being 
excluded. The sign + prefixed to the name of a species indicates that the author 
has not examined actual specimens, but has based his description on the published 
accounts. 
Family LORICARIIDZ. 
Ostariophysi with parietals and supraoccipital united to form a single parieto-occipital 
bone, without suboperculum, symplectic, or metapterygoid; palatine articulating 
posteriorly with the prefrontal and anteriorly with the small rod-like maxillary, which 
bears a barbel ; premaxillaries not protractile, forming the entire upper border of the 
mouth. Caudal vertebrae compressed, with expanded and compressed neural and 
hemal spines ; precaudal vertebrae without parapophyses; coalesced anterior vertebree 
with outgrowths on each side which are suturally united to the cranium, forming, with 
the exoccipitals, two capsules enclosing the two halves of the reduced air-bladder ; 
the last (fifth) bearing a pair of strong ribs, articulating with the first free vertebrae by 
a hinge which permits only of vertical movement ; ribs of the free precaudal vertebra, 
if present, sessile. Nostrils close together, a flap between them; mouth inferior, with 
expanded and reflected lips; jaws with teeth; palate toothless; lower and fourth 
upper pharyngeals with or without teeth; four gills, a slit behind the fourth; pseudo- 
branchie present or absent; gill-membranes broadly joined to the isthmus; four 
branchiostegals. Dorsal fin usually above the precaudal portion of the vertebral 
column; adipose fin often present; anal fin short; ventrals below or in front of the 
dorsal; anterior rays of dorsal, anal, pectoral and ventral, and outer rays of caudal 
simple, often spinous. 
