CHAPTER II 

 EXTERNAL CHARACTERISTICS 



I. GENERAL CONSIDERATIONS. 



1. The Skate. 



The skates are elasmobranch fishes which are highly modi- 

 fied in external form and proportions. They demonstrate, 

 however, the characteristics of the vertebrates in most of 

 their morphological details. The little skate, Eaja erinacea 

 Mitchill, matures at a smaller size than the other common 

 Atlantic skate, the big skate. Raja diaphanes Mitchill, and 

 is the one upon which these directions are based specifically. 

 Most skates have a very similar anatomy and may be dis- 

 sected by the same procedure as is given here. 



The little skate is found along the coastal waters off the 

 Atlantic seaboard of America from Nova Scotia to Vir- 

 ginia. For further information on skates read the section 

 on elasmobranchs in ** Fishes'^ by David S. Jordan and 

 *' Fishes of the Gulf of Maine" by H. B. Bigelow and Wil- 

 liam W. Welch. The following key is compiled from the 

 latter book. 



Determine what species your specimen is from the key. 

 Work out the identification of other specimens on demon- 

 stration. 



2. A Key to the Skates and Rays Common to the 



American Atlantic Coast. 



a-1. The tail without a long dorsal spine. 

 b-1. No distinct caudal fin but two small dorsal fins on the 

 tail. The skates, Family Eajid(Es 



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