6 CALIFOKNIA ACADEMY OF SCIENCES 



The Panama specimens agree well with tlie original description of the species, 

 except in the following respects: — 



(a) Distance from insertion of first dorsal to anterior root of pectoral | (not 

 "about 3") its distance from tip of snout. This discreiJancy is due, however, to 

 an error in the original description. Mr. Barton A. Bean has kindly re-examined 

 the type, and states that the first distance is contained about 2| times in the second. 



(b) Distance between dorsals 23 to 2J times (not "23 times") base of first, 

 and 21 to 3^ times ("a little more than 3 times") base of second. Mr. Bean 

 gives base of first dorsal 21 and base of second dorsal 3^, in the intersi^ace between 

 dorsals. This interval is therefore longer in the type than in any of the Panama 

 si^ecimens. The latter agree, however, with the Mazatlan specimens above mentioned. 



A specimen of M. lamdatus in the United States National Museum (No. 

 46838), taken by the "Albatross" at the mouth of the Mulege River, Gulf of Cali- 

 fornia, has the proportions of the type. The base of the first dorsal, excluding the 

 fleshy hump which precedes the rays, is contained 2g times in the interval between 

 dorsals, the base of the second dorsal 3i times in this interval. It is evident, 

 therefore, that the size and relative positions of the dorsal fins must be used with 

 caution for specific distinction. 



(c) Middle of dorsal base usually midway between axil of pectorals and 

 anterior insertion of ventrals, sometimes very slightly nearer pectorals. In none of 

 the Panama specimens is it nearer the base of the pectorals by a distance equaling 

 the diameter of the eye, as given in the description of the type (slightly less than 

 this in the type according to Mr. Bean). 



Following are dimensions of a Panama specimen: — 



nini. 



Total length 530 



Length of head 95 



Length of snout 43 



Diameter of orbit 17 



Length of spiracle 3-5 



Length of midcjle gill-slit 14 



Distance from ti[) of snout to front of mouth 34.5 



Distance from tip of snout to inner angle of nostrils 27 



Distance between nostrils 14 



Distance between angles of mouth 28 



Distance from tip of mandible to line joining posterior angles of lips 21 



Extreme length of upjjer lip 5.5 



Extreme length of lower lip 8 



Distance from tip of snout to base of pectorals 113 



( Greatest width of ])ectoral base 23 



Outer pectoral margin 71 



Inner pectoral margin 40 



Distal pectoral margin 57 



Axil of pectoral to base of ventrals 107 



Snout to base of \entrals 230 



Outer edge of ventrals 40 



