ORIGIN AND SIGNIFICANCE OF SPINES 63 



mimicry of a plant by an animal to a striking degree. This 

 fish closely imitates a sea-weed (figure 49), and Gunther^^ 

 gives the following description of the spines and filaments 

 on the species Pliyllopteryx eques : " There is a pair of small 

 spines behind the middle of the upper edge of the snout, a 

 pair of minute barbels at the chin, and a pair of long appen- 

 dages in the middle of the lower part of the head. The 

 forehead bears a broad, erect, somewhat four-sided crest, 

 behind which there is a single shorter spine. A horizontal 

 spine extends above each orbit. There is a cluster of spines 

 on the occiput, and from these narrow appendages are pro- 

 longed. On the nape of the neck is a long spine, dilated at 

 the base into a crest, and carrjing a long forked appendage. 

 The back is arched, and on the under side are two deep 

 indentations. The spines on the ridges of the shields are 

 the strongest; they are compressed, are not flexible, and 

 each terminates in a pair of short points. There is one pair 

 of these spines in the middle of the back, and one on each of 

 the three prominences of the abdominal outline; they termi- 

 nate in flaps, which are long and forked. There are also 

 very long compressed flexible spines without appendages, 

 which extend in pairs along the uppermost part of the back, 

 while a single series extends along the middle line of the 

 belly. Small short conical spines run in a single series along 

 the middle line of the sides, and along the lateral edges of 

 the belly ; and there is a pair of similar spines in front of the 

 base of the pectoral fin. The tail, which is about as long as 

 the body, carries the dorsal fin; it is quadrangular, and has 

 sharp edges. It carries along its upper side five pairs of band- 

 bearing spines, which terminate in branching filaments." * 



The Horned Toad Phrynosoma bears considerable resem- 

 blance to the joints of the Prickly Pear, with which it is 

 often associated, and it may be suggested that the likeness 

 both in form and spinescence represents mimetic characters. 



* The artist who copied Giinther's figure for Leunis' " Synopsis der Tliier- 

 kiuide," .3d ed., by II. Ludwij^ (vol. i. p. 770, ISS-")), connected the fish with the 

 adjacent fronds of sea-weed so as to form a single organism. 



