152 U.S. NATIONAL MUSEUM BULLETIN 272 



striations of this rotule often well developed, creating the superficial 

 impression of an indented margin; shaft irregularly covered with 

 large tubercles or blunt spines; terminal knob either smoothly rounded 

 or bearing a small number of recurved minute spines; length range 

 42-58 M, diameter of rotule 16-20 m, of knob 6-8 m, width of shaft 3 M. 



Gemmules scattered through the skeletal meshwork, spherical, 

 ranging in diameter 400-500 m; pneumatic layer only partially de- 

 veloped and comparatively thin, consisting of rather large air spaces ; 

 gemmoscleres embedded in this layer in a manner typical for the 

 genus; foramen produced into a straight and short porus tube, sur- 

 rounded by a circle of slanting gemmoscleres. 



Distribution. — Apparently restricted to Burma. 



Color in life. — Not yet recorded; dry sponge almost black. 



Discussion. — M. vesparioides can be distinguished at a glance 

 from the group represented by M. vesparia by its amphioxous meg- 

 ascleres, which never possess abruptly pointed tips as those oc- 

 casionally found in the latter species. The microscleres, described 

 by previous authors as lacking, are rare in all slides examined, but 

 are present in the type slides revised by Gee (1933c). The marginal 

 indentations of the lower rotule of gemmoscleres, as recorded by 

 Annandale (1908b), were found to be an optical deception. The 

 strong radial reinforcements of this rotule in mature gemmoscleres 

 meet the margin in such a way that a siliceous web of polygonal 

 outline is formed between them. While this web remains very thin 

 the margin of the rotule, although entire, makes the impression of 

 being irregularly incised. 



AI. vesparioides is thus very closely allied to M. vesparia, and 

 future research may yet relegate it to subspecific rank. However, 

 until additional material can be studied it is better to retain its 

 separate specific status, so that possible taxonomic evidence will 

 not be obscured. 



Genus Acalle Gray, 1867 



Acalle Gray, 1867, p. 551.— Gee, 1931e, p. 31.— De Laubenfels, 1936, p. 36.— 



Jewell, 1952, p. 445.— Penney, 1960, p. 32. 

 Tubella Carter, 1881a, p. 98 (part) .—Potts, 1887, p. 250 (part).— Gee, 1931e, 



p. 47 (part); 1932c, p. 43 (part); 1933c, p. 241 (part). 

 (Not Acalle Burton, 1934.) 



Type species. — Spongilla recurvata Bowerbank, 1863. 



Definition. — Megascleres rather stout and cylindrical amphioxea 

 with abruptly pointed or rounded tips, closely approaching am- 

 phistrongyla in appearance; an aggregation of terminal spines often 

 present. 



