FISHES FROM NORTHEASTERN PACIFIC — CHAPMAN 537 



sus, 3.8 to 4 in M. atlanticus); wider interorbital (2.1 in head in M. 

 rugosus, 3.25 in M. atlanticus); smaller pectoral fin (13 rays in M. 

 rugosus, 15 in M. atlanticus). 



M. rugosus can be differentiated from M. nigrofulvus ^ by the shorter 

 head (2.7 in length without caudal in M. rugosus, 2.25 to 2.5 in M. 

 nigrofulvus); more anterior insertion of dorsal (snout to dorsal origin 

 less than from dorsal origin to base of caudal in M. rugosus, greater in 

 M. nigrofulvus); more anterior insertion of anal fin (distance from 

 snout to anal origin less than from origin to base of anal in M. rugosus, 

 greater in M. nigrofulvus). 



From M. unicornis ^ it can be separated by the wider interorbital 

 space (2.1 in head in M. rugosus, 4.66 in M. unicornis); and larger eye 

 (5.8 in head in M. rugosus, about 7.0 in M. unicornis). Finally, it dif- 

 fers from M. triceratops by the lack of the prominently projecting hori- 

 zontal spine anteriorly, characteristic of that species, and the longer 

 dorsal (III, 12 in M. rugosus, III, 10-11 in M. triceratops). 



The portion of the key referred to above, which includes these spe- 

 cies, should be modified as follows to include this species: 



B. A spine on the middle of the snout between the nostrils or ante- 

 rior parts of eyes; origin of anal below posterior half of dorsal. 



1. Origin of pelvic a little in front of pectoral base; caudal ped- 

 uncle 4 to 4J^ times as long as deep; diameter of eye 3^ to Z% 

 in head M. megalops 



S. Origin of pelvic slightly in front of pectoral base; caudal pe- 

 duncle 2 to 2% times as long as deep; diameter of eye S}i to 9}^ 

 in head; head 2 to 2}^ in length without caudal M. macrocephalus 



S. Origin of pelvic below or a little behind pectoral base; caudal 

 peduncle 2J4 to 3 times as long as deep. 



a. Dorsal III, 12-15; origin nearer end of snout than base of 



caudal; interorbital width 2 to 3}^ in head. 

 X. Diameter of eye 7 to S% in head; maxillary extending to a 

 little beyond the posterior margin of the eye; head 2% to 

 2y3 in length without caudal. 

 0. Head 2% to 2^ in the length without caudal; last ray 

 of dorsal behind vertical from middle of anal fin 

 base; caudal peduncle 2% to 2% as long as deep.-M. cristicepg 

 00. Head nearly 3 in the length; last ray of dorsal a little in 

 front of vertical from middle of anal; caudal pe- 

 duncle nearly 3 times as long as deep M. crassiceps 



XX. Diameter of eye 5% to 6>i in head; maxillary extending to 

 below posterior J4 of eye; head 2Jlo to 3 in length with- 

 ■ out caudal; caudal peduncle 2% to 3 times as long as 

 deep. 

 p. Interorbital 2>lo in head; pectoral with 13 rays... M. rugosus 

 pp. Interorbital 3% in head; pectoral with 15 rays M. atlanticus 



b. Dorsal III, 10-12; origin a little nearer base of caudal than 



end of snout; caudal peduncle 2}^ to 2^ times as long as 

 deep; head 2^ to 2^ in length without caudal. 

 X. Interorbital width about 3 or less; eye 6 in head M. nigrofulvus 



« Measurements from Norman, 1929. 



