179 HYDKOIDA. BALK. 



them. The hydrotheca? on the proximal internodes of the 

 gonocladium (which numbered in the specimens examined from 

 six to eleven) are little if at all modified, but the internodes sup- 

 porting them are much elongated, their proximal ends extending 

 some distance beyond the hydrotheca?. In these long internodes 

 the septal ridges were wanting. The crenation of the hydvo- 

 theca-margin varies, being sometimes scarcely indicated. 



In the corbula the ribs widen out into broad leaflets close above 

 their point of origin, so that they do not leave the large inter- 

 mediate openings such as we find in A. 1)11 ardi and many 

 other species ; the openings, where they exist at all, being very 

 small. Sometimes a few small openings are found higher up, 

 where the edges of the leaflets fail to meet. The superior crests 

 or secondary leaflets of the female corbula are sometimes almost 

 as large as those of A. bill ardi, those of the male are usually 

 smaller and strongly curved forward, not so erect as those of the 

 female. The latter average about 6-8 mm. in length, the male 

 about 5 mm. The lateral spurs scarcely project outward, they 

 usually terminate with a small semi-globular sarcotheca, 

 immediately below the hydrotheca, and bear a larger one below, 

 set further back. The corbula is especially characterized by the 

 closely-ranked rows of cup-like sarcothecse. 



Loc. Great Australian Bight, Long 130 40' E, 160 fathoms ; 

 Long. 126 45' E, 190-320 fathoms. 



AGI-AOPHENIA TENUISSIMA, sp. nov. 

 (Plate xxxvii., figs. 1-2.) 



Hydrophyton reaching about fifteen inches in height, polysi- 

 phouic but extremely slender, flexuous, giving off from the flexures 

 small and delicate monosiphonic alternate branches which bear 

 only sarcothecse on the proximal portions ; nodes indistinct, 

 hydrocladia alternate, short, one on an internode. 



Hydrotheca? nearly cylindrical, almost parallel with the inter- 

 node, an oblique rudimentary intrathecal ridge on the adcanline 

 side near the base ; aperture oblique, border with a triangular 

 pointed median anterior tooth, and four teeth, similar but shorter, 

 on each side, back entire, adnate. Two septal ridges in the 

 internode, one opposite the intrathecal ridge, the other opposite 

 the base of the lateral sarcothecse, a third often between them. 



Mesial sarcotheca less than half the length of the hydrotheca, 

 adnate, projecting free portion very short, widely canaliculate. 

 Lateral sarcothecaa small, adnate up to the hydrotheca-margin 

 and scarcely projecting beyond it, canaliculate. Cauline sar- 



