22 6 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



the spots unite to form brassy streaks. In pale phases a narrow dusky line on the 

 head runs back from the eye, and from above the pectoral continues as one of 

 the chief of the longitudinal streaks. At other times the part of this streak before 

 the pectoral stands out as a distinct dark line on the head. A line from the angle 

 of the mouth, also variable in intensity with the general shade of the fish, runs 

 across the cheek parallel with the other, and behind the pectoral is continued by 

 a series of six diffuse dusky spots continuing to the caudal peduncle. A series of 

 ten transverse broken bars, of the average width of the eye, is variably developed 

 across the back, chiefly according to the shade of the substratum. W. H. L. 



The collection contains 4 specimens, 55 to 58 mm. long, which retain the 

 darker color markings essentially as described above for the pale phase. D. VI-12; 

 A. 12; scales 28, in oblique series between origin of anal and base of second 

 dorsal 10. 



Known only from Tortugas, Florida. S. F. H. 



Elacatinus oceanops Jordan 



Common everywhere on large coral heads, on the surface of which it rests or 

 "creeps." It goes sometimes into the empty burrows of Lithophagus, the boring 

 mussel, and it occurs also in some of the gorgonian patches. Wherever found, 

 these small fish slip out from shelter, attach themselves by their ventral disks to 

 other fishes, and "creep" over them, presumably to look for parasites. As many 

 as 6 have been seen together on a Mycteroperca venenosa about % yard long. 

 Epinephehts morio, E. striatus, Lachnolaimus maximus, Pseudoscarus guaca- 

 maia, Haemulon sciurus, Pseud upeneus maculatus, Sparisoma pachycephalum, 

 Acanthurus caeruleus, and Brachygenys chrysargyreus also are sometimes in- 

 spected. 



Some copepods are rather common ectoparasites of fishes. The pursuit of the 

 parasites is with little doubt the business of Elacatinus, but this is more difficult 

 to prove than it would seem. I have not been able to forge the last link. The bold- 

 ness of these tiny fish is almost incredible. They will creep over the teeth of the 

 great Pseudoscarus, or enter the mouths of grunts and groupers and explore 

 them with unhurried movements. Their fitful creeping, or perhaps the nipping 

 of their teeth, is a minor irritation, possibly a sort of tickling, evidenced by a 

 certain tenseness, and shown by broadly gaping jaws and raised gill covers when 

 the inspectors are within the mouth. Their attentions usually continue until the 

 larger fishes grow restless, start up abruptly, or move away and leave them, 

 whereupon they return to their original stations. 



Elacatinus oceanops apparently displays only one color phase, its pattern con- 

 sisting of alternating dark and light blue stripes. Of these the dark ones are 

 three, median, dorsal, and lateral, all running the full length of the body. The 

 dark lateral line passes through the eye and includes the pupil; the light lines 

 touch the eyes as well, and include parts of the dorsal surface. W. H. L. 



The collection contains 20 specimens, ranging in length from 28 to 48 mm. 

 Known only from Tortugas, Florida. S. F. H. 



