No. 434-] 



NOTES AND LITERATURE. 



127 



some Cretaceous or Eocene group of spinous fishes with like numbers 

 of vertebrae 



This view is probably correct. Certainly paleontology and tax- 

 onomy agree in regarding the tropical flounders, percoids, scor- 

 paenoids, and blennies, with few vertebrae, as on the whole more nearly 

 primitive than the cold-water or fresh-water forms which have many 

 vertebra;. At the same time, these tropical forms are the most 

 highly organized, the individual parts of the skeleton being most 

 highly developed. 



We may perhaps regard the tropical forms as having better main- 

 tained their primitive character of a highly developed skeleton, 

 while the arctic and fluviatile forms have become degraded, their 

 parts less developed and increased in number through repetition, 

 this being due to less severity of selection and perhaps the demand 

 for flexibility rather than strength of body. 



In any case, the progressive increase in numbers of vertebras in 

 various groups, as we leave the coral-reef region, is an unquestion- 

 able fact, and must have some cause potent among all fishes. The 

 only cause yet suggested is that of the demands of natural selection 

 in the tropics, with its cessation or reversal elsewhere. But in many 

 groups it is certain that the forms with many vertebra; were not as 

 nearly primitive as the others. D. S. J. 



Boulenger on Selenichthyes. - In the Annals and Magazine of 

 Natural History (Vol. X, pp. 147-153) Dr. G. A. Boulenger takes up 

 the relationship of the large pelagic fish known as the opah or moon- 

 fish {Lampris /una). 



This species has been usually placed, without evident reason, with 

 the mackerel-like forms. It has, however, the very archaic number 

 (15 to 17) of rays in the ventral fins, and these fins are subabdomi- 

 nal in position, although placed well forward. It has the clavicle 

 very large, and behind it, attached to the hypercoracoid, is a very 

 large, flat plate, called the infraclavicle, apparently corresponding 

 in Boulenger's opinion to the interclavicle of sticklebacks. The 

 small hypercoracoid above this plate is on the level of the hypo- 

 coracoid, and out of its normal position. 



Dr. Boulenger makes this fish the type of a new division called 

 Selenichthyes, moon-fishes. This he regards as nearest allied to the 

 Hemibranchii ; and for the two groups, with the Lophobranchii and 

 Hypostomides, he proposes a new suborder, Catosteomi, character- 

 ized by the development of interclavicles. 



