6 THE SKATE 



f-2. No dorsal fins. 



g-1. Tail rounded above, without keel. Sting ray, 

 Dasyhatus marinus Klein. 



g-2. Upper side of the tail with a distinct keel 

 posterior to the long spine. Sting ray, Dasy- 

 hatus hastatus De Kay. 



3. Animal Form. 



Vertebrate animals with few exceptions carry themselves 

 in an horizontal plane, their surfaces always retaining the 

 same relative position. These surfaces are indicated with 

 reference to this position. Locate the following regions of 

 the skate: dorsal, the back or upper side (posterior in hu- 

 man anatomy) ; ventral, the under side (anterior in human 

 anatomy) ; lateral, the sides right and left (throughout this 

 manual right and left refer to the skate's and not to the 

 student's right or left) ; anterior, cephalic, or cranial, the 

 head end (superior in human anatomy) ; posterior, or 

 caudal, the tail end (inferior in human anatomy) ; and 

 median, the middle. 



Adverbs may be formed by substituting a *^d" for the 

 last letter of these terms with the meaning ' ' in the direction 

 of" as caudad meaning towards the tail. Anterior and 

 posterior may be employed to indicate the relative positions 

 of structures with reference to the head or tail, for exam- 

 ple the pelvic fins are posterior to the pectoral fins. 



The head, trunk, tail, and neck when present, make up 

 the axial part of the animal while the fins or limbs make 

 up the appendicular portion of the animal. 



Drawing 1. Draw the outline of the skate from the dorsal view- 

 point indicating the above named surfaces and regions. 



4. Imaginary Planes and Axes. 



Determine these imaginary planes and axes of the skate, 

 a. The sagittal plane or section is any vertical plane 



