On an undescrihcd Ortjan in Liiiniliis. 255 



first two have intimate relations to eaeli otlier, and {h) tlic last 

 three others among themselves ; and some weighty arguments 

 may be adduced to support a division of the faunas of the 

 globe into two primary regions coinciding with the two com- 

 binations alluded to — (a) a C-EN0G-€A and {h) an EoG^A, 

 which might represent areas of derivation or gain from more 

 or less distant geological epochs. 



In connexion with the geographical distribution of fishes 

 there are a couple of empirical facts which are also specially 

 noteworthy. In the order of Teleocephali the Acanthoptery- 

 gian types are vastly preponderant in the tropical and sub- 

 tropical waters, Avhile the jugular Malacopterygian types 

 (e. g. Lycodidoe, Gadidre, &c.) form a large proportion thereof 

 in the polar regions. Further, and it is in the same direction, 

 in Acanthopterygian types the vertebrje are actually or ap- 

 proximately 24, divided between 10 abdominal and 14 caudal, 

 in the great majority of the tropical saltwater species ; while 

 in the cold-water forms (arctic and antarctic) the number is 

 considerably increased. There are many exceptions to this 

 generalization so far as the tropical forms are concerned ; 

 but the tendency in the direction in question is so decided, 

 that while in the warm-water forms of the ty|)ical Scor- 

 pcenince {Sebastosomus, Scorpcena^ &c.) the vertebrfe are 24 

 (A. 10 -f-C. 14), in the representatives which are peculiar to 

 the high north {Sehastes norvegicus and S. viviparus) the ver- 

 tebra are increased in number to 31 (A. 12 + C. 19). There 

 is, however, no apparent physiological or morphological corre- 

 lation between these and other facts, and we have in them 

 perhaps nothing more than interesting cases of iiTclative 

 coincidence. 



XXXIII. — On an undescrihed Organ in Limulus, supposed 

 to he Renal in its Nature. By A. S. Packard, Jun.* 



In dissecting the king crab one's attention is directed to a 

 large and apparently important gland, conspicuous from its 

 bright red colour contrasting Avith the dark masses of the 

 liver and the yellowish ovary or greenish testes, and present- 

 ing the same appearance in either sex. The glands are 

 bilaterally symmetrical, one situated on each side of the 

 stomach an(J beginning of the intestine, and each entirely 



• From an advance sheet of the 'American Naturalist,' communicated 

 by the Author, havinp; been read at the Philadelphia Meeting of the 

 National Academy of Sciences, held in Norember 1874. 



18* 



