82 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.43. 



ACIS SPINIFERA, new species. 

 Plate 13, figs. 2, 2a; plate 21, fig. 1. 



Colony flabellate, straggling in habit, 9.6 cm. in height and with a 

 spread of 10 cm. The main stem is erect, slightly sinuous, 2.5 mm. 

 in diameter. The first branch arises 1.7 cm. from the base. The 

 branches are lateral and, for the most part, sub-opposite, 6 on one 

 side and 7 on the other, about 9 mm. apart on the average, and 1.8 

 mm. in diameter. Some of them give off branchlets to the fourth 

 order. The calyces are thickly emplanted on all sides of the stem and 

 branches, often less than 1 mm. apart. 



The individual calyces are in the form of short cylinders or broadly 

 truncated cones, a typical one measuring 2.4 mm. in height to top of 

 spines and 2 mm. broad at base. The walls are covered with broad 

 scale-like plates, usually broader than long, imbricating. Those of 

 the lower row have free rounded margins which are finely ctenate 

 and overlap the plates of the upper row. The marginal plates have 

 broad bases, the sides of which overlap and are suddenly narrowed 

 distally into prominent spine-like points which surround the margin 

 with a conspicuous crown of points which are somewhat spatulate 

 and often project more than 1 mm. beyond the margin. Usually 

 there are but two rows of plates on each calyx wall, although the 

 edges of the plates of the surrounding coenenchyma may extend 

 somewhat upward over the basal part of the calyx. The collaret is 

 well developed, consisting of two or more rows of transverse spicules. 

 The operculum is regular, composed of three spindles forming an 

 acute angled triangle. 



There are two layers of spicules on the stem and branches. First, 

 an outer layer of heavy plates or scales, usually polygonal, of various 

 shapes and sizes, sometimes with edges nicely fitted; but the larger 

 ones often have the edges more or less imbricated, and are rarely as 

 large as the calyx spicules. Second, a very thin delicate layer of 

 minute rather sparsely distributed spindles. 



Spicules: Mostly polygonal plates of various shapes and sizes, the 

 largest usually curved to fit the calyx or branch, attaining a size of 

 2.5 by 2 mm. The spine scales of the margin are often 2 by 1 mm. 

 There are also spindles from the collaret and operculum, and minute 

 ones from the inner layer of the coenenchyma. 



Color: The colony is tan-brown throughout, and the axis dark 

 golden-brown. 



Locality. — Station 4936; Sata Misaki Light, N. 21° E., 5.7 miles; 

 103 fathoms. 



Tyye-sj}ecimen.—Q2.i. No. 30088, U.S.N.M. 



