GEODIA OVIS. 



169 



The spines arising from the terminal parts of the rays are directed obUquely out- 

 ward and upward. The rays are (without the centrum, when present) 5-12 n 

 long and, at the base, 1-3.2 fi thick. The total diameter of the aster is 11-24 [i. 



The normal sterrasters (Plate 40, figs. 14-18, 24) are flattened ellipsoids, 

 82-92 long, 70-83 /t broad, and 54-61 fx thick. The average proportion of 

 length to breadth to thickness is 100 : 87 : 66. The rays protruding beyond the 

 surface are 3.5-4.5 /t thick and have a terminal verticil of usually five to seven 

 lateral spines. In the sterraster represented in Plate 40, figs. 17-18, the rays 

 surrounding the umbilicus are hardly larger than the others. The umbilicus 

 is 8-15 /i broad and about 10 /.i deep. 



Besides these normal sterrasters a few sterroid forms (Plate 40, fig. 29) of 

 similar dimensions, but with protruding rays 7-8 /x broad, and provided with a 

 much larger number of lateral spines, are met with. I have also observed a 

 larger sterraster with exceedingly thin protruding rays in one of the spicule- 

 preparations, but this I believe to be a foreign spicule. 



This sponge was trawled off southern California, at Station 2975 on Febru- 

 ary 12, 1889, in 34° 1' 30" N., 119° 29' W.; depth 66 m. (36 f.); it grew on a 

 bottom of gravel and broken shells; the bottom temperature was 13.9° (57° F.). 

 A label marked "506 Tetractinellida" was also attached to it. 



As the afferents and efferents are, with little doubt, cribriporal, and as the 

 skeleton is geodine in character I place this sponge in Geodia. 



Its nearest allies are Geodia kilkenthali Thiele, G. (Cydonkmi) miiUeri 

 Fleming, and the sponge here described as G. mesotriaena. 



Geodia kukenthali is distinguished from G. ovis by the very much smaller 

 size of its megascleres, by the absence of small anatriaenes and a particularly 

 well-developed spicule-fur, by the smaller sterrasters, and b}^ the euasters, the 

 largest of which have in G. kukenthali blunt rays while the apparently corre- 

 sponding largest asters of G. ovis have markedly sharp-pointed rays. 



G. miiUeri has, when adult, extensive praeoscular and vestibular cavities, 

 absent in G. ovis, and no such highly developed spicule-fur as the latter. Its 

 megascleres are, although the largest specimens of G. mulleri examined were 

 considerably larger than the specimen of G. ovis, very much shorter than those 

 of the latter, and also its sterrasters somewhat smaller. The dermal asters of 

 G. miiUeri are strongylasters with cylindrical rays and measure 4-10 p. in total 

 diameter, while the superficial asters of G. ovis are 11-24 /x in total diameter 

 and many of them have more or less conical rays. The remarkably large oxy- 

 asters with stout, conic, sharp-pointed rays of G. ovis have not been observed 



