124 LAWRENCE M. LAxMBE ON 



Plocamia Manaarensis, Carter. 

 (Plate IL, figs. 11, 11a— g.) 



Diclyocyliiidrus Manaarensia, Carier. 1880. Ann. and Mag. Nat. Hist., series 5, vol. vi., p. 37, pi. iv., tigs, la — g. 



One small specimen incrusting the entire surface of a fragment of shell 15 mm. long 

 and 10 mm. broad. The sponge has a thickness of about 1 mm. Colour, in spirit, brownish- 

 gray. Texture firm. Surface even, strongly hispid. Dennal membrane thin, spiculous. 

 The characters of the oscula and pores have not been ascertained. 



Skeleton. — Composed of a fairly regular reticulation of dumb-bell-shaped spicules (tylota) 

 supporting a dermal arrangement of outwardly pointed stylote and tylostylote spicules. 

 The dermal styli are large and project some distance beyond the general surface ; the tylo- 

 styli are much smaller and are collected round the bases of the styli. 



Spicules. — (a) Megaselera ; of four kinds: (1) Stout, slightly curved, smooth tj'lota : 

 (Plate II., fig. 11) with very decidedly marked terminal heads which appear to have their 

 outer ends slightly roughened ; the shafts of these spicules are thickest at the centre ; up to 

 0-10 mm. in length, average thickness 0-008 mm. Among the tylota one was observed 

 that had the shaft strongly spined. (2) Large, smooth, slightly bent styli (Plate IL, fig. 

 11a) thickest near the base and gradually tapering to an acute point ; up to 0"687 mm. 

 long and from 0-016 to 0-019 mm. thick. (3) Slightly curved, smooth, sharply pointed 

 tylostyli (Plate IL, fig. lib), thickest a short distance from the distinctly marked, rounded 

 head which appears to be, like the heads of the tylota somewhat roughened or minutely 

 spined ; about 0-183 mm. in length and from 0-009 to 0-013 mm. thick. These spicules 

 project only slightlj- beyond the surface of the sponge and are much more numerous than 

 the large styli at whose bases they are arranged in groujis. (4) Very slender, smooth tylo- 

 styli (Plate IL, fig. lie), with an average size of 0-176 by 0-003 mm. ; found at the surface 

 scattered in the dermal membrane. {b) Microsclera ; (1) Minute, palmate isochelse (Plate 

 IL, figs, lid, lie) 0-013 mm., in length. (2) Slender toxa (Plate IL, figs, llf, llg) 

 0-065 mm. long, measured in a straight line between the terminal ends ; found only in 

 small numbers. In a vertical section a number of spherical gemmules were observed near the 

 base of the sponge ; they were reddish-brown in colour and about 0-052 mm. in diameter. 



There is so very little difference between the spiculation of the incrusting Californian 

 sponge and the erect branching one from the Gulf of Manaar, that it is thought advisable 

 to refer the former to Carter's species although there is so great a difference in outward 

 form between the two and the localities where they were obtained are so widely separated. 

 The Californian sponge although incrusting may be in a young stage of growth ; additional 

 specimens are needed to show the form and variations in growth of mature individuals. 



The spicules of the type specimen as given by Carter (op. cit) are : — (1) Acuate spicules 

 {styli}, 0-64 mm. long ; (2) shorter acuate spicules (tylostyli), 0-38 mm. long ; (3) hair-like spicules 

 (slender tylostyli], about 0-24 mm. in length ; (4) spicules with inflated extremities (tylota), 

 0-24 mm. long ; (5) tricnrvate spicules (toxa), 0-Obl mm. in length; (6) equianchorate spicules 

 (isochelœ), 0-01 mm. in length. 



Locality. — California. 



Phakellia ventilabrum, Johnston. 

 Halichondria vintilahrum, Johnston. 1842. British sponges, p. 107, pi. vii. 



