189 



areas have often small, found acropetal spines. The cryptocyst very tuberculous 

 and furnished with closely situated pores. 



The avicularia, which are extremely rare, have a long, narrow, tongue-shaped 

 mandible. 



Spicules. The length of compasses found varies between 0,053 and 0,186™'"-, 

 and the length (height) of the curves between 0,033 and 0,039™"- The 

 latter, which are much higher than broad, have a peculiar stirrup-like shape, 

 and the legs are rectangularly bent at the end, while at the same time the 

 median knot is unusually strongly developed and conically pointed. It must 

 however be remarked that the zooecia in the colonies examined have lost most 

 of their spicules. 



This form has partly been found on a Tridacna, the locality of which is 

 unknown, partly on a Haliotis from the Andaman or Nicobar Islands (de Roep- 

 storfF). 



Var. B. 



(PI. VI a, figs. 1 a-1 f). 



The zooecia, the length of which varies from 0,598 to 0,731""", are usually 

 rectangular, rarely furnished with somewhat angularly bent or curved lateral 

 margins. The adoral areas have no spines, and the cryptoc5'st is less tuberculous 

 and has fewer pores. 



The avicularia are rather numerous and have a broad irregularly vasiform 

 or lyriform mandible, the mandibular cavity of which hardly occupies one-third 

 of the entire breadth and is bounded by two subparallel chitinous margins at 

 the point concurrent. 



Spicules. Length of compasses varying from 0,046 to 0,292™™ , and that of the 

 unusually smal curves from 0,013 to 0,033™™- They differ from the curves in Var. A. 

 in being less high, in having a less developed median process and a more curved 

 bending of the point of the legs. 



Of this form I have examined some fragments of hollow colonies and some 

 small one-layered laminse from Torres Straits (Haddon), belonging to the Museum 

 of Zoology at Cambridge. 



Var. C. (tubifera). 



(PI. VI a, figs. 2 a-2 e). 

 The zooecia, the length of which may vary from 0,532 to 0,731™™, are fre- 

 quently rectangular, sometimes however furnished with somewhat angularly bent 

 or curved lateral margins. The adoral areas have no spines, and the cryptocyst 



