178 



attain the size of the laller, have most often a strongly developed distal ciypto- 

 cj'st, and outside the opercular arch the mandible has in most cases wider or 

 narrower, marginal expansions. The avicularia also generally olTer good specific 

 characters. With regard to the structure of the gonozooecia and the ocrcia re- 

 ference may be made to the separate species. 



A single genus Thalamoporella. 

 Synopsis of the species. 



1) Spicules Ijoth in the form of curves and compasses. 



2) The opesiular outgrowths generally meet the basal wall in a 

 continuous, transverse line, which lakes up the entire breadth of the 

 wall; (the operculum without continuous proximal chitinous sclerite; 

 the avicularian mandible vase-shaped; curves very slender; the largest 



not much shorter than the longest comjiasses) T. lioliclui Orlmann. 



2) The ojjesiular outgrowths never meet the basal wall in a conti- 

 nuous line, which takes up the whole of its breadth; (the basal wall 

 of the polj'pide-tube formed by the basal wall of the zocecium): 



3) The two legs of the compasses are different, one being curved 

 inwards and iiooked at the end; (the operculum with continuous proxi- 

 mal chitinous sclerite; the surface of the zoa'cia divided into 3 — 4 



areas, separated by sutures) T. Jerooisi Hincks. 



3) The legs of the compasses are not different. 



4) The avicularian mandible has the form of an isosceles triangle 

 with somewhat convex sides. Of the two opesiular outgrowths generally 

 only one reaches the basal wall; (the operculum of older zooecia with 

 continuous proximal chitinous sclerite, or the latter is only broken for 



a short distance) T. Rozieri Aud. 



4) The avicularian mandible is never triangular, but more or less re- 

 gularly tongue-shaped or vase-like; the two opesiular outgrowths both 

 reach to the basal wall, which they never meet in closed curved lines; 

 (the proximal margin of the operculum on each side with a short 

 chitinous sclerite) T. (iniunlalit n. sp. 



1) Only compass-like spicules occur; 



5) The proximal margin of the zorecial aperture is straight or 

 almost straight; 



6) Only a single opesiular outgrowth reaching to the basal wall; 

 the proximal margin of the opesiula is generally furnished with a row 

 of partially furcate spine-like processes, and similar processes may ap- 



