442 PROCEEDINGS OF THE NATIONAL MUSEUM vol. S3 



There are various reasons for believing that shallow-water sponges 

 attain distribution laterally rather slowly, or at least that they are 

 profoundly restrained by environmental barriers. In 1932 (de 

 Laubenfels, 1932) I found considerable difference between the coastal 

 sponges of central and southern California, and I can report subse- 

 quent (as yet unpubhshed) investigation in the field indicating even 

 greater differences between the sponges of California and those of the 

 coast only a few hundred miles north of that State, and similarly 

 great differences between the sponges of California and Lower Cali- 

 fornia. At the Pacific end of the Panama Canal there are tre- 

 mendously high tides and at the Atlantic end almost no tides at 

 all, whereas at the Atlantic end the ocean temperature is considerably 

 higher than at the Pacific. A great difference between the faunas of 

 the two regions was therefore to be expected. Such a difference might 

 be due to the different ecological conditions or to independent evolu- 

 tions during a geologically long period of separation. Similarities 

 between the faunas of the two regions would be less easily explained. 

 A marine connection until recent times might be assumed, although 

 other reasons for this assumption are scanty. Perhaps throughout 

 whole geologic ages sponge species neither vary much (in an evolu- 

 tionary sense) nor perish as species, nor migrate away from their 

 established locations. 



Sixteen species of sponges were collected at or near the Pacific end 

 of the Panama Canal, and 21 species were taken at the Atlantic end. 

 Ten species were found only on the Pacific side and 15 only on the 

 Atlantic, while six occurred in both localities. Of these sLx, only 

 two are cosmopolitan; four are distinctive of this part of the world! 



The Porifera of the Caribbean end show close relationship to the 

 West Indian faima. An astonishing number of them were new 

 species, no less than seven, or 33 percent. In general the Pacific 

 coasts of Central and South America have been exceedingly little 

 studied, and it might be expected therefore that more new species 

 would have been found in that region, but such was not the case. 

 Only five species on the Pacific coast proved to be new, again a third 

 of the number collected. Searching over the rocks exposed at low 

 tide at Panama City yielded nine species and proved astonishingly 

 similar to collecting near Plymouth, England. Four out of the nine — 

 Haliclona permollis, Halichondria panicea, Microciona atrosanguinea, 

 and Oscarella lobularis — are forms common to both localities. Of 

 other species occurring nearby, Toxadocia proxima is Arctic, Pseudo- 

 suberites sulcaius is Antarctic, and Aplysilla glacialis is both Arctic 

 and sub-Antarctic. 



Attention is called particularly to the dissimilarities between the 

 Panama sponge fauna and that of the Pacific coast of North America 

 in general. Of the sponges recorded from California, at least 11 per- 



