THF> MORPHOLOGY OF THE UHKU.OSTOMATA . 267 



oblique rows passing entirely across the branch in two inter- 

 secting directions. Orifices apparently connected by a 

 continuous, brown, transparent epitheca, a short distance 

 below Avhich the frontal surface of each zooecium is strength- 

 ened by a system of irregular calcareous bars, which tend to 

 radiate from a point in the middle of the base-line of the 

 operculum towards the proximal and lateral sides of the 

 zocecium. Basal side of the branch similarly covered by an 

 epitheca, which each zocecium reaches along a longitudinal 

 line narrower and shorter than itself. Opercula large, 

 dimorphic, the ordinary form about as long as broad (250 to 

 270 ju), the others with a broader base (290 to 320 /<). Both 

 kinds of opercula are strengthened by a conspicuous 12-shaped 

 sclerite. The distal margin of the vestibule is provided with 

 a chitinous lip, which is overlapped during retraction by the 

 large lateral flanges of the operculum. Ovicells not found, 

 and probably absent. 



The material was discovered by Mr. T. Whitelegge under 

 rock ledges, at low-tide line, Watson's Bay, Port Jackson, 

 and in Middle Harbour, Port Jackson. Although part was 

 in spirit, its condition was not sufficiently good to make a 

 complete anatomical investigation possible. 



The genus Euthyris was founded by Hincks^ for a new 

 species, E. obtecta, from North Australia. The generic 

 name, introduced '' to suggest the idea of higher structure " 

 in the operculum, is particulai'ly appropriate to E. clathrata, 

 in which the operculum is specially complicated. The two 



1 ' Ann. Mag. Nat. Hist.' (.5), x, 1882, p. 104. In 1871 Quensteilt (' Petie- 

 faktenkunde Deutschlands,' Abtli. I, Bd. ii, p. 412), in discnssinrr the struc- 

 ture of a Brachiopod, used the following words : — " Man konnte sie dalier 

 wohl Euthyris aber nicht Athyris nenneu." I have not been able to ascer- 

 tain that Queustedt made any further use of the word Euthyris, and he 

 does not even refer the species he is discussing to that genus. It appears, 

 therefore, that he was not in reality proposing a new genus (and he certainly 

 did not define it), but was merely making a verbal criticism of the name 

 Athyris, Although Euthyris (Quenstedt) is mentioned by Zittel in his 

 well-known ' Handbuch d. Paleeont.' (i, p. 684) as a synonym of Spirigera, 

 it does not seem to me that it has any valid claim to recognition. 



