On some 'Dynast'idod from Tropical America. Vol 



usually hunts by smell and not by sight, and when food is 

 put into the tank it does not swim straight towards it, as 

 many other fishes {e. g., cod) do, but rushes wildly about with 

 its pelvic fins spread out at right angles to the body until it 

 brushes against it. The evidence, however, is not suffieient 

 to decide whether these organs are purely tactile or whether 

 they are used in the same way as similar structures in the 

 higher vertebrates. 



My best thanks are due to Professor M'Intosh for his 

 kindness in supplying material and for many helpful 

 suggestions. 



EXPLANATION OF PLATE V. 



Fig. \. Left pelvic fin of O/vi^ mmtela, 5 milliin. in lengtli. 



Flfj. 2. Ditto, 20 milliin. in lenj^-th. 



Fti/. 3. Ditto, 23 millim. in length. 



Fif/. 4. Ditto, 32 milliin. in length. 



Fiff. 5. Transverse section of pelvic fin of Onus, 23 millim. in length. 



ep., epithelium ; //•., dermal fin-rays ; ?i.c., nerve-covd ; pff., 



pigment. 

 Fir/. 6. Pelvic fin of a specimen 98 millim. in length. 

 Fig. 7. Transverse section of the foregoing. 

 Fig. 8. Free ray of ditto in section, more highly magnified. 

 Fig. 9. Epithelium of ditto, high power. 

 Fig. 10. Sense-organ. 



Figs. 1, 2, 3, 4, and 6 are not drawn to scale. The actual size of these 

 is represented by the line underneath each. 



Reference letters. 



Js.=basement membrane. ?;;;;. = Ma]pighian layer. 



cf. = cuticle. n.c. = nerve-cord. 



f/r. = dermal fin-ray. s.o.= sense-organ. 



eyj. = epithelium. ^. = connective tissue. 



XVII. — Notes and Descriptions of some Dy nastidai from 

 Tropical America, chiejiy supplementary to the ' Biolojjia 

 Centr all- Americana.'' \iy Gilbert J. Arrow, F.K.S. 



I. — On Central- American Species of the Genus Cyclocephala. 



Althougu thirty-five described species of Cyclocephala are 

 enumerated by H. W. Bates in the ' Biologia Ccntrali- 

 Americana,' this probably forms scarcely more tiian a fraction 

 of those actually inhabiting Central America. The British 

 Museum collection already contains about a dozen additional 

 species, and, as certain corrections have to be made to the 



