Apsil 13, 1906.] 



SCIENCE. 



587 



the gill region in breathing but is taken in at 

 the mouth and forced backward over the gills 

 and out in a backward direction. Secondly, 

 there are certain types of fishes which possess 

 no pectoral fins and yet manage to keep up 

 their supply of oxygen. Thirdly, there are 

 certain fishes which live upon the bottom, like 

 the skates, or even buried under the sand, as 

 the flounders, which are unable to make any 

 such use of the pectorals and yet breathe 

 without difficulty. Lastly, it is a point of 

 observation without a single exception in my 

 experience that the ordinary, actively swim- 

 ming type of fish when resting on the bottom 

 does not move the fins at all. Observations 

 of several years' standing, on fishes in and 

 out of aquaria, have recently been supple- 

 mented by careful studies at the New York 

 Aquarium on many different types of fishes, 

 both fresh water and marine, and the result 

 is invariably as above stated. 



On the other hand, all the fishes that I have 

 observed use the pectorals when they are sus- 

 pended in the water. Moreover, other fins 

 are often brought into use at the same time. 

 Thus the elongate pike {Lucius) and gar 

 (Lepisosteus) are seen to move the pelvic fins 

 slowly, coordinately with the pectorals, and 

 short-bodied forms such as the butterfly-fish 

 (Chcetodon) move the pectorals and caudal, 

 while in species intermediate in form the 

 caudal, anal and dorsal may, any or all, be 

 used in addition to the paired flns when sus- 

 pended in the water. This array of facts 

 makes it quite clear that the function of the 

 pectorals when the fish is stationary is that 

 of equilibration and not the removal of water 

 charged with carbon dioxide. 



It is impossible to formulate a rule for the 

 pectoral fins which will cover all cases, since 

 in the more or less aberrant species this fin 

 may be used for creeping on the bottom or 

 even for progress on land or in the air, or it 

 may enter into the formation of a sucking 

 disc, or rarely may be absent; but as far as 

 the usual swimming type of fish is concerned, 

 the following uses are most in evidence: 



Guiding and balancing the body in swimming; 

 To act as a brake in arresting the progress; 



Equilibration when suspended stationary in the 



water, and 

 Locomotion, either forward or backward. 



The pelvic fins are generally used much in 

 the same way as the pectorals, though of less 

 importance. The vertical fins may assist the 

 caudal in locomotion or the pectorals in bal- 

 ancing. In terete types of fishes the dorsal 

 and anal seem to have much the same function 

 as a centerboard on a boat, to prevent the 

 body from slipping sidewise through the water 

 when the caudal portion is flexed in making 

 the stroke. In fishes of this type which have 

 had these fins removed the body is seen to 

 wriggle to a greater extent than in those which 

 possess the fins. 



In conclusion, I wish to say that no one 

 appreciates better than the writer the highly 

 adaptive character of the fins, especially those 

 of teleosts, and that any one who searches for 

 exceptions will find them — it would probably 

 be much more difiicult to find two species in 

 which all the fins are used in exactly the same 

 manner — and yet I believe that the general 

 functions of the fins are about as above out- 

 lined. Raymond C. Osburn. 



Columbia University, 

 January 18, 1906. 



COLUMBIA FIELD WORK IN 1905 INTERCOLLEGIATE 

 FIELD COURSES IN GEOLOGY. 



During the latter part of May and early 

 part of June, 1905, a party of nine graduate 

 students from the department of geology, 

 Columbia University, under the guidance and 

 direction of Professor A. W. Grabau, made a 

 somewhat extended field trip through New 

 York State, visiting and studying in consider- 

 able detail many of the type localities and 

 typical developments of the Paleozoic forma- 

 tions. The object of the trip was, by actual 

 field work, to make each student familiar with 

 the general appearance and lithological char- 

 acter of the various formations as they occur 

 in the field, as well as their stratigraphical 

 relation to one another and to the underlying 

 crystalline rocks, and by personal collecting, 

 to make him familiar with the characteristic 

 fossils of each formation. Whenever oppor- 

 tunity was afforded a study was also made 



