THE SPONGES. 59 



shorter, — common length about 240 /x. Spicules are quite frequently 

 found in which the umbel is degenerate, the teeth remaining as minute 

 structures, Fig. 1, a, b, c, Plate 7. Sometimes ihe merest rudiments 

 of the teeth, so small that they are apt to escape notice, remain on the 

 otherwise smooth head, and very occasionally a clavula with a perfectly 

 smooth head is found. In certain cases all the teeth degenerate except 

 one, which is fairly well developed, 



A very few gastral clavulae of the type shown in Fig. 3, Plate 7, were 

 found. The umbel teeth are long and with a distinct spiral twist. The 

 stalk is much longer than in the common gastral clavulae, and is slightly 

 curved. In the spicule figured, the stalk bore a lateral spine which was 

 absent in the others found. Only half a dozen of these spicules were found 

 in as many preparations, and they would naturally be looked upon as 

 foreign, were it not that they occupy the same position with respect lo 

 the pentacts as do the other clavulae. This spicule is closely similar 

 to the peculiar clavula of Farrea convolvulus F. E. Sch. (Schulze, 1899, 

 Plate XVI.), the stalk of which bears 3 to 5 lateral spinee. Its very occa- 

 sional occurrence here has the greater interest for the existence of a 

 species in which the characteristic spicule is so closely similar. 



In the type (Schulze, 1887), the predominant form of gastral clavula 

 has a smooth anchor-like head with 4-8 lono; teeth. But forms havinij 

 a terminal umbel with numerous teeth, which overarches a swelling, occur 

 and may predominate. 



Farrea davigera F. E. Sch. (1887, p. 287, Plate LXXV.) resembles the 

 subspecies here described in having smooth club-shaped dermal clavulae, 

 but differs from it in habitus, in having anchor-like gastral clavulae, and 

 in having a second peculiar form of dermal clavula. 



Farrea occa is a widely distributed species. F. convolvulus F. E. Sch. was 

 taken 32° 49' N., 117° 27' 30" W., at a depth of 656 m. 



