Australian Hydro ids. 355 



<^orbula that these cups are notably different from the ordinary 

 .•sarcothecae ; on the first leaflet or two they are usually quite 

 .similar, both in form and size, to the sarcothecae of the ribs; the 

 •succeeding ones are progressively broader, to about the middle of 

 ^he corbula, while at the distal end they are again reduced to 

 •nearly the size and form of the ordinary sarcothecae. Often after 

 attaining the maximum size the next one is bifurcated, forming 

 i>wo cups, as shown by Billard, who recognises that in this case 

 ithey are true sarcothecae. Uusually the spur of the first leaflet (as 

 well as of the supernumerary one which is generally present) bears 

 only one sarcotheca instead of two; the next spur may have both 

 Ihe upper and the lower sarcotheca about equal in size, and tlien 

 "the gradual increase of the superior receptacles commences. The 

 transition from the undoubted sarcotheca.e at the ends of the corbula 

 to the largest of the cups near the middle is so gradual that I can 

 find no line of demarcation such as we should expect if some of 

 Ihem were sarcothecae and others hydrothecae. The large cups are 

 very irregular in the form of the border, but they have a deep 

 Tnarginal sinuation, a character common to all the sarcothecae, but 

 Tiot found in hj'drothecae. 



According to Billard the spurs support inferiorly a pair of sar- 

 -cothecae, which he considers represent the laterals of the assumed 

 .hydrothecae; I cannot find any instance of this in my specimens, 

 in which the inferior sarcotheca is single, and situated centrally, 

 Tiot laterally. In one or two instances I have seen this sarcotheca 

 bifurcated, one branch then being above the other. Ihe inferior 

 •sarcotheca is united by a web of perisarc to the superior cup. 



The corbulae may very probably present sexual differences, but 

 I have no means of ascertaining whether this is so, as all tlie 

 •corbulae observed by me were from the same colony. The sex was 

 ■not determinable. 



Cladocarpklla, Bale. 



I have followed Nutting in regarding the genus Cladpcarjyus as 

 •characterized by the possession of phylactocarps which are limited 

 to a single one on a hydrocladium, always springing from the base 

 •or the proximal internode; consequently on meeting with a species 

 Avith the phylactocarps not limited to that position, but occurring 

 on several internodes of the same hydrocladium, I proposed for 

 it the genus ChNlovarpdla. The distinction is not very strong, 

 and it is to be observed that Allman's original diagnosis of the 

 .-genus Cladocarpus is wide cnougli ta embrace such forms, and that 



