188 



-with lateral margins curving outwards, and has likewise two lateral expansions, 

 which are separated from the mandibular cavity by the triangular opercular 

 arch. The marginal portion of the mandible is chitinized to an unusual degree. 

 This species, which incrusts a red alga from Madagascar, belongs to the Mu- 

 seum of Zoology at Cambridge, and has been kindly lent me for examination of 

 Dr. S. Harmer. 



Thalamoporella granulata n. sp. 



(PI. Via, figs. 1, 2; PI. VI, fig. 5). 



The length of the zooecia may vary between 0,532 and 0,93™™- The aperture, 

 the size of which may be contained 3 '/a — 4 times in the whole length of the 

 zocecium, has a broad and deep sinus, which is generallj' separated from the 

 remaining semi-circular or semi-oval part by strongly developed hinge-teeth. The 

 proximal margin of the operculum has on either side an extremely short chitinous 

 sclerite. The two indistinctly marked adoral areas are usually slightly developed, 

 but may be furnished with small, round acropetal spines. The two opesiulae 

 show as a rule no great difference in size, and the opesiular outgrowths both 

 reach the basal wall, meeting it in two open hooked lines, which may be equ- 

 ally large. The frontal wall of the polypide-tube is not very deeply depressed, 

 and the cryptocyst, which has a strongly developed, crenulated or tuberculated 

 marginal part, is on the whole of its frontal surface more or less strongly tuber- 

 culous. Numerous, rather large pores. 



Spicules occur both in the shape of compasses and curves, and particularly 

 the latter show rather a wide range of variation. The smaller spicules are also 

 found between the cryptocyst and the covering membrane. 



The ooecia, which are without pores, Jiave a rounded triangular outline and 

 a somewhat projecting aperture. The gonozooecia are of about the same size as 

 the ordinary zooecia, and the chitinous arch of' the operculum is not far from 

 the margin. 



The avicularia, which may reach and even exceed the length of the zooecia, 

 have a strongly developed distal cryptocyst. The mandible is sometimes narrow 

 and tongue-shaped, sometimes broad and more or less regularly lyriform or 

 vase-shaped. 



Var. A. (stapifera). 



(PI. VI, figs. 5 a-5 e). 

 The zooecia, whose length generally varies from 0,798 to 0,93™'" , are most often 

 of a rounded hexagonal form, frequently unusually broad and flat,. The adoral 



