536 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 83 



Distinctive characters and relationships. — In practice no difficulty will 

 be found in identifying specimens belonging to tliis species. Only 

 one other species, hildebrandi, is now laiown to occiu- within the range 

 of ingenfi. The differences between the two are discussed under the 

 account of hildebrandi (p. 579), which is saliently distinct from ingens. 



This species differs from all others of its subgenus treated herein 

 in its large size and in the fact that the upper ridges of the tail and 

 trunk overlap on three segments as often as on two, possibly even 

 oftener on three, whereas in the other species the normal overlap is 

 on two segments with an overlap on three as a rather infrequent 

 individual variation . In this respect ingens forms a transition between 

 Hippocampus proper and the subgenus Macleayina. 



While there is no doubt that ingens is quite distinct and no author 

 ever questioned its distinctive nature, it is remarkable that it shows 

 no structural characters by which it may be sharply delimited from 

 some other American or European species of Hippocampus, which 

 possibly are not even closely related to it. This furnishes an illus- 

 tration of the difficulties encountered in properly distinguishing the 

 species of Hippocampus by the ordinary morphological methods. In 

 its slender body, long snout, color pattern, and tendency for the tuber- 

 cles to become obsolescent with age it closely approaches or agrees 

 with reidi, differing in having more numerous caudal segments and 

 dorsal rays; but the two species closely approach each other in those 

 characters even in the comparatively few specimens studied. When 

 a large specimen of reidi is compared with specimens of ingens of 

 similar size — specimens of such length may be considered to be only 

 of medium size in ingens — the former appears markedly different on 

 account of its obsolescent tubercles; but in full-grown specimens of 

 ingens the tubercles on the trunk also become rather obsolescent, 

 especially in full-grown males. 



As far as the structural characters are concerned, ingens is even 

 nearer to gtitfulatus from the Mediterranean, or multiannularis from 

 the Atlantic coast of Europe, closely agreeing with those two sub- 

 species in the number of caudal segments, pectoral rays, and dorsal 

 rays and being nearer to the former in its dorsal rays and nearer to 

 the latter in its caudal segments. It differs from both in having 

 a longer snout and, on the average, a slenderer body and a characteris- 

 tic profusion of small dark spots. The length of the snout possibly 

 will also be found to intergrade when larger series are measured. It 

 is also closely related to hudsonius from the Atlantic coast of North 

 America, ingens differing chiefly in the color pattern, but in structural 

 characters the two species more or less overlap, although the averages 

 or frequency distributions are decidedly different. While ingens, in 

 general, differs from hudsonius in its structural characters in approxi- 



