NO. 1 . DICKINSON : SPONGES OF GULF OF CALIFORNIA 13 



The principal fibers are 50 fi in diameter and contain 4 spicule rows. The 

 secondary fibers are difficult to make out and contain only occasional 

 spicules. Spicules are also scattered in confusion outside the fibers. 



Holotype. — AHF no. 4. 



Type locality. — San Jaime Banks, off Cape San Lucas, Mexico ; Lat. 

 22° 50' 30'' N, Long. 110° 15' W; old coralline algae, granite rocks. 



Distribution. — Gulf of California. 



Material examined. — 

 Sta. 618-37 San Jaime Bank 3-3-37 150 m 



Reinarks. — The San Jaime Banks are not in the Gulf of California; 

 but their location near the mouth, plus the fact that the sponge fauna 

 from there is, in most cases, also found in the Gulf proper, makes the 

 location an integral part of the region as far as this study is concerned. 



There is no other Rhizochalina reported from the west coast of the 

 Americas. In fact, none has been reported from the American zone of the 

 Pacific Basin. The nearest relative appears to be R. sessilis Kirkpatrick, 

 1900, from the East Indies. This had a pyramid to fingerlike shape, but 

 its oxeas are only 14 by 372 fx. This is a large difference. The principal 

 tracts are much larger and contain 10 rows of spicules, while the second- 

 ary tracts are about the size of the principal tract in the Gulf species and 

 contain 3 rows of spicules. R.oleracea Schmidt, 1870, which is the geno- 

 type, is somewhat similar, but has even smaller spicules than R. sessilis. 

 It is West Indian. 



Family Plocamiidae Topsent 



Genus PLOGAMIA Schmidt 



Plocamia karyoka, new species 



Plate 17, Figs. 33, 34; Plate 18, Fig. 35 



Diagnosis. — This is an encrusting sponge, rather firm in consistency, 

 with branching protrusions often several mm in diameter, making up the 

 bulk of the specimen. The preserved material from the Gulf is, of course, 

 drab. 



The endodermal structure Is interesting in that its ascending columns 

 with connecting spicules give it a ladderlike appearance under the low 

 power of a microscope. 



The principal spicules are subtylostyles with microspined heads; size 

 18 /A by 340 /*. Secondary spicules, strongyles with microspined heads; 

 size 16 [x by 200 fi to 22 fi by 175 /x. Interstitial spicules, tylostyles; size 

 12 /t by 200 /A to 3 /A by 160 ju,. First microsclere, palmate isochelas of a 

 peculiar twisted form; length 10 /x to 17 /x. Second microsclere, toxas; 

 length 18 /A to 80 JU,. 



