326 • Transactions. — Zoology/. 



The branchial siphon is short, and has its edge six-lobed. 

 The tentacles were not observed, but the endostyle is extremely- 

 undulating (fig. 2, en.). There are four rows of stigmata, with 

 wide transverse vessels and narrow longitudinal. The trans- 

 verse vessels are slightly muscular. (Fig. 11 is from C. i)ers])i- 

 cuus, but the differences are slight.) 



The stomach is thin-walled and globular, but not large. 

 The relations of the various sections of the alimentary canal 

 were not satisfactorily settled, but the course of the rectum is 

 easily made out in zooids removed from the colony and 

 mounted entire, by means of the faecal pellets. There is a 

 long atrial siphon near the anterior end of the body ; its rim 

 is also six-lobed (fig. 2, at.s.). 



Numerous ova of varying size were found near the intes- 

 tinal loop (fig. 2, ov.). Others were seen in special brood- 

 pouches springing from the peribranchial cavity, and a few 

 tailed larvae were also met with occupying a clear transparent 

 pouch through which the structure of the almost equally 

 transparent embryo could be easily discerned. 



Note. — j\Iy first conviction with respect to the calcareous matter 

 found in this and the following species was that it could not be cal- 

 careous, for I found that in hydrochloric acid the disclike spicules 

 dissolve readily, while the other forms do not. But on leaving a thin 

 section in the acid (1-per-cent. solution) for five hours all traces of the 

 deposits were removed. This anomaly I believe to be due to — (1) the 

 different nature of the calcium crystals, and (2) the difficulty of pene- 

 trating the middle test-layer, 



Cystodytes perspicuus, n. sp. (?). Plate XXX. 



A single small colony was obtained in July. I am not yet 

 convinced of its specific value, but shall consider it as such 

 for our present purpose, and shall here merely point out the 

 differences noted. 



In external features there is considerable resemblance. 

 But this form is slightly thinner, averaging 4mm., and is quite 

 colourless and transparent except for the white capsules. 



The spicules present no differences, but, although calcareous 

 fibres were present, no calcareous trees were found comj)arable 

 to those of C. aucklandicus , their place being taken by the 

 even more peculiar crj^stalline forms shown in fig. 5. 



Histologically the tests are identical, except as regards the 

 calcareous deposits. 



The branchial siphon is shorter than in the former species, 

 as is also the atrial siphon. The buccal tentacles are short 

 and blunt. 



The branchial basket exhibits the same features as does 

 that of its predecessor, but the muscular ridges of the trans- 

 verse vessels are much more strongly developed. 



