teeth are present only in juvenile A. nilpes less 

 than 50 mm. 



The only differences in color pattern between 

 A. vulpi's and A. ncmopfrra are the markings 

 on the snout. In A. rulpcs there is a median in- 

 verted U-shaped mark on the tip of the snout 

 instead of an anchor-shaped mark and there 

 are no lateral black dashes. 



Both species are sympati-ic, but there is evi- 

 dence that they may be partially segregated 

 ecologically. This is discussed elsewhere in this 

 study. 



For purposes of identification and compari- 

 son the most significant differences between A. 

 nemoptcra and A. viilpes are summarized in 

 the following key: 



la. — Vertebrae 77 to 80. Dorsal rays 21, rarely 

 20. Pelvic rays 9. Pectoral rays 16 to 18, 

 usually 17. Branchiostegal rays 13 or 14, 

 rai-oly 12 or 15. Lateral line scales 78 to 84, 

 usually 80 to 82. Last ray of dorsal fin pro- 

 longed into a filament reaching beyond vei-ti- 

 cal from tip of pelvic fin (except in speci- 

 mens smaller than 75 mm. in standard 

 length). Last ray of anal fin prolonged into a 

 filament longer than anal fin base (except in 

 specimens smaller than 75 mm. in standard 

 length). Maxillary reaching beyond vertical 

 from anterior margin of orbit. 



Albula nemopti'va 



76.— Vertebrae 69 or 70. Dorsal rays 18 or 19, 

 usually 19. Pelvic rays 10, rarely 9 or 11. Pec- 

 toral rays 17 to 19, usually 18. Branchiostegal 

 rays 10 to 14, usually 11 or 12. Lateral line 

 scales 68 to 77, usually 71 to 73. Last ray of 

 doi-sal fin not prolonged into a filament reach- 

 ing beyond vertical from tip of pelvic fin. Last 

 ray of anal fin not prolonged into a filament 

 longer than anal fin base. Maxillary not 

 reaching to vertical from anterior margin 

 of orbit (except in specimens smaller than 

 70 mm., standai-d length). 

 Albula riil])cs 



EARLY STAGES OF DEVELOPMENT 



Seven larval albulids, collected with four 

 juvenile A. nemoptera in Caledonia Bay, 

 Panama (LACM 20467) are tentatively identi- 

 fied as metamorphosing larvae of A. ncmnp- 

 frra. This identification was determined by 



256 



comparing these larvae (table 12) with as 

 many of A. vulpes of equal size as could be 

 found in Alexander (1961). To avoid misintei- 

 pretations resulting from slight differences in 

 measuring and counting, six larval A. ridprs of 

 comparable size from St. Andrews island 

 (UMIM 5928) were included as a control. 



The presumed A. nemoptera larvae differ 

 from those of A. rnlpes in predorsal length, 

 preanal length, and number of myomeres (table 

 12). These differences are confirmed bv the 



I'vBi.K I'J. Cotiipiinsoii of iHitdiitorphDmiHj Utniic of All)iil;i 

 iifinnptera? and A. vulpes iif simitar size 



ll'roporlioiis in Ihoiisuiidllis of the standard IciiKtIil 



.Standard length 

 (nun.) __ _ 



I'ri'ddrsiil length 



I'rcanal lenpth 



NiiinhiT r>f 

 niyonieres 



.1. nemoptera? 



Caledonia May, 



I'unama. LACM 



204(17 (7 



specimens) 



liaitge 



*.;)- 4«.» 



i -S15 

 922 -971 



119 - 74 



.1. vnlfiet 



Alexander, 19(il: 



38-40 (S 



specinu'ns) 



Mean- Range \\tean 

 .11.3! 57.0- 4S.5' 51.4 

 796 1 81)5 -S3U 818 



70.8 



St. Andrews 



I.sland. Colombia. 



r.MIM .5928 



(0 specimens) 



Kan tie 



.111.2- 48.0 

 S07 -825 

 9.111 -975 



(17 - (19 



I 



Mean 

 .12.2 

 814 

 9(18 



1)8.2 



comparison of juveniles of A. vulpes and A. 

 nemoptera (table 13). In both species the num- 

 ber of vertebrae is higher than the observed 



TMti.iv i:i. ('(iiiifiiirisdu of jiifenitcH of .\\\iii\:i Mciiin|itiT.i dii'l 

 .\. vulpes of similar size 



I Proportions in tliiMi.sandlhs of the standard lontitlil 



Cliiirai-IiT 



Standard lenKth (mm.) 



Predorsal lennth__ 



I'ri'iiial leniilh 



NiinUjer of vertebrae... 



.1. nemoiitera 



Caledortia Bay, 



Panama. I.AC.M 



204(17, 204(18 



(5 specimens) 



. vnlftcs 



(illaiialio. Ciiha. 



r.MIM 7.18 



15 specimens) 



Mean 

 42 

 481 



812 

 73.0 



number of myomeres, and this difference is 

 probably due to the difl^culty in discerning the 

 last, very closely api^roximated myomeres 

 especially in A. nemoptera. The apparent 

 greater number of vertebrae in juveniles (table 

 13) is, on the average, three or four units 

 greater than in adults (table 11) as counted 

 from the radiographs, and this diflference may 



U.S. FISH AND WILUIJKE SERVICE 



