138 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.8 



3. Dorsal side with numerous scales (14 between oral and anal 

 scales) but comparatively few feet, easily overlooked. Dorsal 

 side with typical hourglasses of lacelike structure and large 

 towers which in older individuals become shortened, so that 

 they are thimble shaped. Sole with 4-holed buttons and plates 



with marginal knobs ; holes comparatively small 



4. Thyonepsolus hancocki, new species 



1. Thyonepsolus nutriens H. L. Clark 

 Plate 26, Figs. 1-5 



Thyonepsolus nutriens H. L. Clark, 1901, p. 169; 1901a, p. 491, text 



figures. — Deichmann, 1930, p. 193 (passim); 1937, p. 174. 

 Psolidium nutriens Ludwig, 1904, p. 689. 



Diagnosis. — Small form (length of sole 2 cm.) ; distinct sole with 

 numerous feet in 3 crowded bands. Dorsal side with numerous small 

 scales, lacking in the midline (except in very young individuals), feet 

 numerous, and external layer of spicules well developed. Spicules in sole 

 perforated plates (0.10-0.15 mm.) and smaller flattened baskets (0.06 

 mm.) ; feet with end plate and supporting rods. Dorsal side with scales 

 and perforated plates (0.18 mm.) often slightly concave, and hourglass- 

 shaped bodies (0.10 mm.). In most individuals a number of huge tower- 

 like deposits (0.20-0.30 mm.) numerous in young individuals where the 

 other types of external spicules may be scarce. Dorsal feet with rudimen- 

 tary end plate and curved perforated plates or rods in the walls. Introvert 

 and tentacles with perforated plates or buttons and rods. 



Type.— M.C.Z. 



Type locality. — Pacific Grove, California, in tide pools. 



Distribution. — From the type locality southward, Santa Cruz Islands, 

 off Santa Barbara, California. 



Depth. — Tide pools to few fms. depth. 



Specimens examined. — The type and about 50 from various localities. 



The following material examined from the Allan Hancock Expedi- 

 tions : 

 11-32. Conway Bay, Indefatigable Island, Galapagos, shore, January 

 12, 1932, 1 specimen. 



Remarks. — A single specimen in the Allan Hancock Expeditions has 

 been identified with this species, but the label says Station 1 1-32 ( ?) which 

 is Conway Bay, Indefatigable Island, Galapagos, shore. 



