SEA-FISHERIES LABORATORY. 333 



men, which, is a small ray measuring 4-J inches across the 

 wings. On either side of the head is a deep notch which 

 causes the pectoral fins to stand well out from the body. 

 The dorsal side of the specimen is figured, but I have 

 indicated the position of the gill openings by dotted lines. 

 The median line of symmetry is disturbed, so that the 



Fig. 24. Ilaia clavata, showing .arrested development of the pectoral 

 fins. Reduced. 



head of the fish is bent to the left side by about -J inch. 

 So far as can be seen without dissection, the external 

 borders of the notches are formed by the propterygia, and 

 the malformation is evidently due to the assumption, 

 during development, by the latter skeletal structures, of 

 a position which is much more nearly related to the 



