42 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



ReTYiarhs. — The lack of spicules thicker than 9/^ is one of the most 

 distinctive features about mutahilis, the great rarity of the anatri- 

 aenes perhaps even more so. The most of the species of this genus 

 have strongly radiate architecture, sigmoid microscleres, and papil- 

 late surface. 



Although it is found concurrently with the massive form, I 

 incline to believe the clavate form the juvenile of the massive. It 

 is strongly suggestive of Tetilla radiata Selenka (1879, p. 467), from 

 Rio de Janeiro, which also lacked microscleres, and is probably its 

 closest relative. 



TETILLA ARB de Laubenfels 



Tetilla arb de Laubenfels, 1930, p. 30. 



BoIot7jpe.—V.S.^M. No. 21490: B.M. No. 29.8.22.44. 



Type locality. — Pescadero Point near Carmel, Calif., July, 1925, 

 intertidal, collected by the author. Numerous specimens were exam- 

 ined, all from central California, as this is a rather common species 

 there. It grows usually on the under sides of overhanging rocks, but 

 I found one specimen lying unattached under a bowlder. 



Description. — Shape, subspherical. Size, up to 5 cm high, 8 cm 

 in diameter. Consistency, firm, cartilaginous. Color in life and 

 when preserved, drab. Oscules, diameter about 3 mm; surrounded 

 by a palisade of densely packed spicules. Pores, not evident. Sur- 

 face, superficially hirsute, with a spicule plush about 3 mm high. 



Ectosomal specialization, corticate, 0.5 to 1.4 mm thick. I see no 

 fibers in it, no tangential spicules, but abundant microscleres. Most 

 of the spicules that project beyond it seem to be protriaenes. They 

 might be considered as chiefly cortical. The outer portions of the 

 cortex contain many cells with conspicuous dark granules. Endo- 

 somal structure, cartilaginous, crowded with radially arranged spic- 

 ules. The axial region is almost solid spicule. Histological details: 

 As is common, the cells proper are well under 15/x in size. There are 

 present, scattered in the flesh of at least one of the specimens of 

 Tetilla arh, large bodies about 60|Li by 100/a in cross section, resem- 

 bling cells. These may be large ova or small embryos. 



First spicules, filiform oxeas (fig. 19, B, C) ; size 9/Lt to 50/a in 

 diameter; length certainly several millimeters, probably 2 or 3 cm. 

 Second spicules, anatriaenes (fig. 19, Z>, E) ; chords, 50ju, to 90/a; 

 rhabds, usually but 6/i, to 12/x in diameter; length, probably more 

 than 10 mm. Their cladomes usually lie just below the surface. 

 Third spicules, protriaenes (fig. 19, F, G, H, I) ', chords. Sju to SOfx 

 rhabd diameter, 2fji to 12/i, ; length up to at least 32.4 mm as based on 

 one of which I was able to make accurate measurement. In the 

 sponge they are so densely packed it is difficult to say where one 

 begins and another ends; disengaged they are usually broken. 



