548 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 83 



segment; or, upper ridges of tail and trunk usually overlapping on 

 two segments, often on three. Trunk segments usually 11 (in six), 

 sometimes 12 (in the two specimens noted above as having the 

 penultimate trunk segm.ent completely novemangular). Caudal 

 segm.ents usually 36 or 37, varying 36 to 38.^^ Dorsal rays usually 

 18 or 19, varying 17 to 19. Pectoral rays usually 14 or 15, varying 

 13 to 15. Tubercles on upper ridge of trunk conspicuous, but rather 

 short, intermediate in development between guttulatus and hippo- 

 campus. Coronet variable, medium to rather low, double bony 

 hump in front of it usually lower than and distinctly not continuous 

 with it. Trmik of medium depth; snout conspicuously short. Avail- 

 able specimens wdthout any filaments. Color faded in available 

 specimens, traces of white elongate spots or short lines on opercle 

 and trunk of two specimens. (See tables 1 and 2 for counts and meas- 

 urements.) 



Distinctive characters and relationships. — H. europaeus is likely to 

 be confused with multiannularis, which occurs in the same region 

 with it, and the two have apparently been so confused by most 

 authors. The difference between them has been pointed out under 

 the account of the latter (p. 541). This species is also near to hippo- 

 campus from the Mediterranean, agreeing with it in the short snout 

 but differing in having more numerous caudal segments and dorsal 

 rays, a slenderer body (see tables 1 and 2), and conspicuously better 

 developed tubercles. In the two meristic characters they intergrade, 

 but in the relative depth there are no intergradients in the specimens 

 measured, although such may be found when larger numbers are 

 measured. The range of variation of each species and the relation 

 between europaeus and hippocampus still remain to be determined. 

 It is possible that their geographic ranges overlap and that in the 

 region where both occur some difficulty may be found in referring 

 occasional specimens to their proper species (see discussion of uncer- 

 tain specimen on p. 572). 



H. europaeus is even nearer, in its structural characters, to hudsonius 

 from the American coast, especially to its northern population, than 

 to any European species or subspecies. It differs chiefly from 

 hudsonius in having a shorter snout, and to a lesser extent in a slen- 

 derer trunk and fewer pectoral rays; but in the latter two characters 

 there is more or less intergradation (see table 1 and compare tables 

 2 and 3). The typical color pattern of europaeus is apparently 



" In the brief description of the type specimen 1 stated that it has 39 caudal segments. A reexamination 

 of the specimen after I gained considerably more experience in counting the caudal segments shows that 

 38 is probably the correct number, but it is diffleult to determine with absolute accuracy whether it has 

 38 or 30 unless the specimen is to be dissected. Since what appears to bo the last segment is slightly longer 

 than usual, it was thought to represent two segments. However, according to the method herein employed 

 in counting the segments, it should be recorded more properly as having 38 caudal segments (see p. 504). 



