18 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.11 



Material examined. — 

 Sta. 555-36 Angel de la Guardia Island 3- 8-36 40 m 



Remarks. — This sponge is not close to any other member of the genus. 

 The genotype Myxichela tawiensis is perhaps the nearest relative, but it 

 has bipocilli and the toxas are more than twice as large. Lepthoclathria 

 hoplotoxa is similar in the size of the microscleres and the same type of 

 megascleres, although they are much smaller, but it is a thin encrusting 

 sponge instead of massive. 



Genus MYXILLA Schmidt 



Myxilla mexicensis, new species 



Plate 24, Figs. 47, 48 ; Plate 25, Figs. 49, 50 



Diagnosis. — This sponge is massive, 10 cm by 7 cm by 6 cm, and 

 amorphous. The color in alcohol is pinkish drab, the consistency mediocre. 

 A distinct dermal membrane about 100 /x, thick covers rather extensive 

 subdermal cavities and is easily detachable. The surface of the sponge is 

 superficially smooth. Occasional openings 3 mm in diameter and irregu- 

 larly placed are found. The endosome is very coarse in microscopic 

 structure. 



Coring spicules are very small anchorate chelas, which are usually 

 12 /A but sometimes only 10 /a long. Sigmas are also present, as a rule about 

 14 /x in length. An occasional sigma 32 ju, was found in one specimen, but 

 these do not appear to be proper. 



Holotype. — AHF no. 9. 



Type locality. — 0£E San Francisco Island ; 60 m ; corallines. 



Distribution. — Gulf of California. 



Material examined. — 

 Sta. 513-36 San Francisco Island 2-24-36 60 m 



Sta. 520-36 Agua Verde Bay 2-27-36 15 m 



Sta. 607-36 San Lorenzo Channel 3-21-36 48 m 



Sta. 642-37 Espiritu Santo Island 3- 8-37 55 m 



Remarks. — All the sponges of the Myxillidae, which are massive, have 

 megascleres that are very close to one another in type. They are distin- 

 guished as to genus by the combination of microscleres present ( or absent) 

 and as species largely by the size range of the spicules. It is on this basis 

 that the above species is established. The microscleres are exceedingly 

 small for their type for the Myxilla. In fact, they represent an extreme 

 for the genus. M. agennes de Laubenfels, 1930, apparently the nearest 

 relation, differs in having sigmas about 33 \x. and chelas about 27 /a. This 

 sponge is from California. M. rosacea Lieberkiihn, 1859, has sigmas 49 /a 

 and chelas 30 )u,. In addition, the styles are spiny throughout their length 

 instead of only on the head. 



