1895.] NATURAL SCIENCES OF PHILADELPHIA. 191 



is regarded by Pfeffer 11 as a proof of the bipolar distribution of 

 Orangon. I have doubted the correctness of Pfeffer's opinion in 

 this view, 12 and have pointed out that the examples of bipolar 

 distribution of crustácea enumerated by him do not correspond exactly 

 to the facts known, except in the case of Or. antárcticas. But 

 neither in this species, is, I believe, a bi polarity of the genus 

 probable. Or, antarcticus is the nearest allied to Cr. franciscorum 

 and this fact induces me to suppose that a connection between the 

 northern and southern range of Orangon is present along the west 

 coast of America from California to Chili, and in the same manner, 

 I believe, there is a connection from the European seas along the 

 western coast of Africa to the Cape of Good Hope, the locality of 

 Cr. capensis. Litoral species of Crangon have not yet been recorded 

 from the western coasts of America and Africa, but I hope that 

 further investigation will demonstrate the presence of this genus in 

 both localities, and thus strengthen my theory. 



Supposing my theory to be correct, the range of Crangon 

 would be a northern circumpolar one, partly containing circum- 

 polar species, partly species confined to the northern parts either 

 of Pacific or of Atlantic. Some species descended into the deep 

 sea to a depth of about 900 fathoms and coifld propagate more 

 southward. Along the west coasts of Africa and America, owing 

 to the cooler temperature of the seas on these coasts, the rauge of 

 Crangon could extend to the southern hemisphere, crossing the 

 tropics. 



The range of the genus Xectocrangon, the nearest allied of Crangon, 

 agrees wholly with that of the northern species of Crangon: one 

 species, Xectocrangon lar, is a true arctic-circumpolar one extending 

 very little southward (the most southern locality recorded is Nova 

 Scotia), the other, Xectocrangon alaskensis, is restricted, as we know, 

 at present to Alaska. 



The genus PoniopMlus, the first of the series, representing the second 

 branch of development arising from Pontocaris, has a nearly cosmo- 

 politan horizontal distribution, but the several species are wholly dif- 

 ferent from each other. The greatest number of species, like Crangon, 

 is found in the litoral of the cooler seas of the northern hemisphere, 



11 Pfeffer. Die niedere Thierwelt des antarctischen Ufergebietes. — Internat. 

 Polarf. Deutsch. Exped. II, 1S90. p. 520-572. 



12 Ortmann, Jenaische Denkschriften, VIII, 1894, p. 77. 



