M. Fries on the Genus Syngnathus. 101 



for distinguishing the species. If this character has been ob- 

 tained from a comparison of the same sex I would acknowledge 

 its justness, but not otherwise ; for the rule, that the anal aper- 

 ture in the female is at a far greater distance from the snout 

 than in the male, holds good in all pipe fish, and especially in 

 S. cequoreus is this distinction between both sexes very re- 

 markable. The age must also be taken into consideration ; for 

 if we compare a young specimen with an old one, both of one 

 sex and the same species, we find in the former the distance 

 rather shorter than is the case in the latter. 



2. It is worthy of remark, that although the anal aperture 

 in the male is situated closer to the snout than in the female, 

 we still find the same number of plates, and of rings formed of 

 these, in both sexes, both between anus and head as well as 

 between anus and caudal extremity. Hence follows that the 

 number of plates affords a very good character for the species 

 if their enumeration were not connected with some difficulty 

 and uncertainty, as they partly merge into one another, and in 

 living and quite fresh specimens it is almost impossible to di- 

 stinguish them. 



3. The form of the body is quite different in the two sexes. 

 We may take it as a rule, that the body in the female is higher 

 and broader, that there is a raised keel or ridge on the back as 

 well as under the belly, which the male, which has a more 

 cylindrical trunk, possesses only traces of under the belly. Al- 

 though the trunk in living specimens of both sexes scarcely 

 exhibits any traces of three ridges running on each side, with 

 the exception of one species, where they are more prominent ; 

 yet they are apparent in all, if they have been laid in spirits 

 for some time or dried. 



4. The length of the head in proportion to the rest of the body, 

 in all small and long fishes, is not constant ; disregarding the 

 difference which age brings with it in this respect. As in young 

 individuals the head is always found relatively longer, we also 

 meet in the Syngnathi with considerable individual differences. 



5. The position of the dorsal fins stands always in a rather 

 constant proportion to the anal aperture, and if not fixed too 

 minutely affords a very good character, which holds good in 

 both sexes. 



