8 



ous substance of the a\is shows .1 crystalline appearance, there are no indications 



th.it u is composed of fused spicules. The concave si. les of th< section ccirrespond, of 



rrooves for the primary canals, and the number eight seems significant as being 



the original number <'t' these canals, corresponding to the eight inlermesenterial chambers of 



primary polyp >>t" the colony or branch. The central area is marked bj an axial nuclear 



t, from which many lines radiate toward the periphery of the area 



The homy nu. les are hour-glass shaped, in longitudinal section, their ends being concave 



lor the insertion of the convex ends of the calcareous internodes. At the line of juncture there 



n irregular mass of horny projecrions alternating with the calcareous material, giving an 



anchorage that binds the node and internode together. There are no calcareous spicules in 



the nodes 



Spicules. These are all quite small, and of several forms. All are modifications of 

 short tuberculate spindles. Doublé spindles, dumb-bell shapes, doublé heads, crosses and densely 

 tuberculate oval forms predominate. All are closely tuberculate, and most of them show a 

 median, constricted smooth girdle. There are a few doublé crosses and spindles with regular 

 whorls of tubercles. 



• lor. The specimens in alcohol are a tan brown, the dried specimens being- darker 

 brown. A\is white, with the horny nodes dark hom brown. 



General distribution. This species has been reported from the Indian Ocean, and 

 parts *<\ the tropical eastern Pacific. The form reported from the Mediterranean is in all 

 probability not this species or genus. 



This species is quite variable, and specimens differ much according to size and age, the 

 larger sterns and branches having the "moniliform" appearance that has led some authors to 

 describe several species on the basis of what appears to be merely variëtal ditierences. 



Many of the dried specimens were originally much larger than the one described; but, 

 owing to their excessive brittleness, they are so badly broken up that the original dimensions 

 can not easily be ascertained. 



2. Isis reticulata new species. (Plate I, figs. 2, 2a: Plate V, fio-. 2). 



Stat. 273. Anchorage off Pulu Jedan, East coast of Aru Islands. 13 meters. Sand and shells. 



Colony much broken up. the specimens consisting of large and small fragments all from 

 the same station. General habit loose and straggling. much less inclined to the formation of 

 dense tufts than in Isis hippuris. The thickest stem found is 7 mm. in diameter, and the horny 

 internodes are almost entirely obliterated. being indicated by darker color alone. The longitudinal 

 are continuous over the calcareous and horny joints, the latter being but slightly con- 

 stricted. The first calcareous internode is 1 cm. long, the next 1.6 cm., the next 2 cm., and 

 ng a hranch a little above its middle. Further up the horny nodes are sharply constricted, 

 ed and about 2 mm. in length. The 1 nam hing is straggling, and there are occasional 

 istomoses of branches. There is a distinct tendency toward a flabellate form of colony. The 



