Nizinski et al,: Separation of Ammodytes amencanus and A dubius in western North Atlantic 



243 



Methods 



Approximately 1500 specimens from a range of loca- 

 tions (North Carolina to Greenland) along the western 

 North Atlantic coast were examined in this study (Fig. 

 2; Appendix 1). Total number of gill rakers were 

 counted on the first arch on the right side; pectoral fin 

 rays were counted on the left. Dorsal and anal ray 

 counts were obtained from radiographs. The anterior 

 1-3 pterygiophores of the dorsal fin may have no asso- 

 ciated fin ray; therefore, dorsal fin counts began at the 

 first visible ray. Several cleared and stained specimens 

 were examined to verify counts obtained from 

 radiographs. Precaudal, caudal, and total vertebral 

 counts were also taken from radiographs. The first 

 caudal vertebra was defined as the centrum bearing 

 the first elongate hemal spine. Total vertebral counts 

 exclude the hypural plate following the practice of most 

 recent workers on the genus. 



Sand lances possess distinctive rows of oblique folds 

 of skin or plicae which occur on the lateral body sur- 

 faces and are lined on the undersides by cycloid scales. 

 The rows of plicae characteristically extend from an 

 area above the pectoral fin base to the caudal pedun- 

 cle. Plicae length and the angle of direction at which 

 plicae run are highly variable near the head and tail 

 (Fig. 3). Total plicae counts proved difficult to make 

 and were not repeatable. Therefore, we modified plicae 

 counts to begin with the first plica posterior to the first 



Figure 2 



Distribution o{ Ammodytes aintru-anua and /I. dubius in western 

 North Atlantic based on specimens examined for this study. 



.__^ , ' . , ;/ >i fi J >U i, .. ' . — , , „ . 1' I . ' ..  .■ — L — : 



Figure 3 



Drawing of Ammodytes dubius shows how phcae were counted (between arrows). The irregular plicae present anteriorly and posteriorly (see 

 insets) were not counted. 



