290 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
eye, lower jaw slightly projecting; isthmus very broad, gill-opening not reaching farther forward 
than vertical opercle; preopercle smooth with concealed spine; caudal peduncle compressed, least 
width 3.75 in its least depth, which is 2 in head; teeth in broad bands, outer ones of lower jaw 
somewhat enlarged; dorsal outline rising gently from snout to origin of spinous dorsal; ventral line 
relatively straight; scales very small, those on head embedded and cycloid, those on back, belly, and 
anterior part of sides cycloid, on posterior part of body ctenoid; lower portion of preocular and cheek 
naked, upper portions with small embedded scales. Fins moderate; origin of spinous dorsal nearer 
tip of snout than posterior edge of soft dorsal by a distance equal to diameter of orbit; distance between 
spinous soft dorsal slightly greater than diameter of orbit; dorsal spines flexible; dorsal and anal rays 
when depressed barely reaching rudimentary caudal rays; caudal fin regularly rounded; tips of ven- 
trals reaching halfway to origin of anal fin; tips of pectorals extending slightly beyond tips of ventrals. 
Color, dark, marbled with darker and lighter; under parts dirty- whitish; fins dark like body, 
bordered with white, especially the dorsals and anal. 
The moron reaches a foot in length and is a good food-fish. It is found on the east coast of 
tropical America from Cuba to Rio Janeiro, in fresh and brackish water, and is generally common. 
Only two examples (6.5 and 8.5 inches long) were seen in Porto Rico by us; they were obtained in 
the San Juan market January 15, and probably came from the mouth of the Bayamon River. 
Eleotris guavina Cuvier & Valenciennes, Hist. Nat. Poiss., XII, 223, 1837, Martinique. 
Guavina guavina, Jordan & Evermann, Fishes of North and Middle America, 2198, 1898. 
Genus 136. ELEOTRIS (Gronow) Bloch & Schneider. 
Body long and low, compressed behind. Head long, low, flattened above, without spines or 
crests, almost everywhere scaly. Mouth large, oblique, lower jaw projecting. Lower pharyngeals 
rather broad, teeth small, bluntish. Preopercle with a small concealed spine below, its tip hooked 
forward. Branchiostegals unarmed. Eyes small, high, anterior; isthmus broad. Post-temporal bones 
very strongly divergent, their insertions close together, the distance between them about two-thirds 
the narrow interorbital space, and less than one-seventh length of head; top of skull somewhat elevated 
and declivous; interorbital area slightly convex transversely; the dorsal fins . well separated, first of 
6 or 7 flexible spines; ventrals separate. Scales moderate, ctenoid, 45 to 62 in longitudinal series; 
vertebrae (pisonis) 11 + 15. 
Found in tropical seas, entering fresh waters. 
а. Teeth subequal, those of inner or outer series enlarged. 
б. Cheek entirely sealed. 
c. Teeth of inner series of each jaw enlarged. 
d. Scales in a median series 40 to 61, in a cross series 12 to 20. 
e. Eye large, 5 to 6 in head; scales 40 to 44, — 12 to 14 amblyopsis 
ee. Eye small, 8 in head; scales 51,-20 abacurus 
dd. Scales in a median series 57 to 66; in a cross series 18 to 24 pisonis, 244 
66. Lower half of cheek naked; scales 61 perniger 
244. Eleotris pisonis (Gmelin). “Moron.” 
Head 2.9; depth 3.75; eye 7; snout 5; maxillary 2.75; mandible 2.75; interorbital 3.6; preorbital 
10; pectoral 1.4; ventral 2; caudal 1.4; D. vi-9, the longest spine 3 in head, the longest ray 2.5; A. i, 8, 
the longest ray 2.3; scales 57 to 63,-19 to 22; vertebrae 11 + 15. Body stout, not compressed; head 
broad, depressed, tapering forward; mouth large, oblique, maxillary reaching posterior border of pupil; 
eyes high up; isthmus moderately broad, gill-openings extending forward somewhat beyond angle of 
preopercle; preopercle with a strong concealed spine at angle, directed forward; no teeth on vomer or 
palatines; teeth on jaws in wide villiform bands, outer series somewhat enlarged; lower pharyngeals 
broad, triangular, without fringe, teeth bluntish; branchiostegals 6; gillrakers 2 + 9, very short; caudal 
peduncle compressed, its least width one-third its depth, which is 2 in head. Fins moderate; origin of 
spinous dorsal about midway between tip of snout and tip of dorsal rays; space separating dorsals scarcely 
more than half orbit; dorsal and anal rays not reaching base of caudal; ventrals inserted somewhat 
behind insertion of pectorals, their tips reaching halfway to origin of anal ; pectoral reaching beyond 
ventrals. Scales small, crowded anteriorly, embedded on nape, head, and cheeks, ctenoid only on sides. 
Color, dark-brown or blackish; sides with faint narrow dark lines alternating with narrow light 
ones; fins with dark wavy lines. 
