195 



proximal and inward, and the opesiular outgrowth touches the basal surface in 

 an open, hooked, curved line. The proximal margin of this opesiula has a series 

 of from 3 to 7 distally-pointing spines, partly more or less branched, partly 

 single, and both its margins are moreover furnished with larger or smaller 

 laminate processes of varying shape, which generally point more or less obliquely 

 towards the opesial cavity and are more rarely on a level with the opening of 

 the latter. They maj' be curved, lobed, sinuous or even furnished with branched 

 processes (fig. 5 b). On account of these marginal expansions the entrance to the 

 opesial cavity is often made very narrow and in some cases by partial fusion of 

 two such opposite portions reduced to a small hole. The cryptocyst, which in 

 older zooecia may have a raised margin which is rather broad especially in the 

 proximal part of the zooecium, is, as in Th. Jervoisi, divided into four, sometimes 

 three segments, as the distal or the proximal one may have fused with one of 

 the lateral parts. The ojjesiular opening cjuite separates the distal area from one 

 of the lateral ones, and the area opposite that of the opesiula is in most cases 

 furnished with from 2 to 5 partly single, partly branched spines. With the excep- 

 tion of a very tuberculous belt immediately on the proximal side of the aperture, 

 tubercles only occur in very small numbers, the greatest number being found in 

 the proximal area, which is also the only one to show a few small pores. 



Spicules. Only compasses occur, the length of which varies from 0,033 to 

 0,133™™-, and of which a great many are more or less strongly curved. 



Ooecia are not found. 



The avicularia are rather uncommon and much smaller than the zooecia. 

 They have a small triangular mandible with a rather long, linear terminal part. 

 A larger or smaller part of the subopercular area is furnished with a very thin, 

 not deeply depressed crj'ptocyst lamina ending in a dentate margin. 



In one place a smaller number of narrow, abnormal zoa'cia were found, the 

 cryptocyst of which consisted partly of a generally very broad, and sometimes 

 strongly prominent marginal portion, the inner edge of which is broadly crenu- 

 lated, and partly of a depressed, more or less tuberculated median portion. The 

 marginal portion, divided by sutural lines into numerous small areas corresponding 

 to the crenulations may attain so great a breadth that its two lateial halves may 

 coalesce sometimes in the distal and sometimes in the proximal part of the zoa*- 

 cium. In the distal half of the zocrcium there is frequently a somewhat vary- 

 ingly shaped, round or oval aperture without operculum. 



A small colony of this Australian species was kindly placed at my disposal 

 by the late Mr. Peal. 



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