NO. 1 DICKINSON : SPONGES OF GULF OF CALIFORNIA 49 



600 fji in the largest spicules. The smaller rays are 12 ju. by 200 fi. Oxeas 

 are also present. A typical size is 27 fx by 700 /x. This specimen shows the 

 typical ascon development of the genus. 



Holotype. — British Museum. 



Type locality. — East Africa. 



Distribution. — Cosmopolitan. 



Material examined. — 

 Sta. 584-36 Concepcion Bay 3-14-36 8 m 



Remarks. — The shape of this sponge is not very symmetrical ; in fact, 

 it tends to be leafy. It is quite probable that this specimen may not be 

 conspecific with Jenkin's sponge, as the spicule sizes are even larger than 

 he reported, but there are such an enormous number of species Leucoso- 

 lenia that it seemed better to identify this specimen with Jenkin's species 

 rather than erect a new species where the differences are not clear cut. 



SUMMARY 



1. A detailed, systematic study of the sponges of the Gulf of Cali- 

 fornia is recorded here. The only sponge collecting in the region for scien- 

 tific purposes, previous to the Allan Hancock Pacific Expeditions, was 

 done on the Albatross Expedition in 1891. Three specimens so far as 

 known were reported from the Gulf on that cruise, all from relatively 

 deep water. 



2. Three classes, 10 orders, 30 families, 56 genera, and 67 species 

 of sponges are represented in the Allan Hancock Foundation collection of 

 sponges from the Gulf of California. 



3. Twenty-six species and one genus of sponges, new to science, 

 are described in this paper. 



4. The Demospongia are the dominant type found in the Gulf of 

 California. Less than 4 per cent of the sponges collected from the region 

 are Calcarea, as against a normal expectancy of 10 to 15 per cent for 

 shallow water forms. This is probably due to the fresh water poured into 

 the confined area of the Gulf of California from the Colorado River. 



5. There is evidence that the Gulf of California presents near 

 optimum conditions for sponges because species density is very great, while 

 population density per species is low. 



6. The waters of tropical and subtropical America in both the 

 Atlantic and Pacific Oceans should be considered as a single faunal unit 

 in spite of present-day isolation because of the number of "gem.inate" and 

 "identical" species in the two areas. 



C 



