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vvhich is not quite terminal. The tentacles are about 12 in number. The tentacle-sheath may 

 lie either to the right or to the left of the intestinal limb of the alimentary canal; no uniformity 

 in this respect being discoverable, even in the zooecia of a single longitudinal row. The pharynx 

 is short; and in the retracted condition its proximal end forms the extremity of the first limb 

 of the alimentary canal. The oesophagus, formed of transparent cells, is long and passes distally. 

 It is remarkable for its width l ), which exceeds that of the caecum of the stomach. The stomach 

 and its caecum are noticeably small, and together do not greatly exceed the length of the 

 rectum, which is well developed. The parietal muscles are small and delicate, the fibres occurring 

 singly. The retractor-muscles form a conical group, embracing the proximal end of the lophophore. 

 Reproductive organs are absent. 



Waters 2 ) has given a useful list of the number of tentacles believed to be characteristic 

 of various species of Alcyonidium. None of these records are so low as 1 2 except those of 

 Lamouroux and Fleming (both referring to A. gelatinosum; which, according to Hincks, has 

 15 — 17 tentacles); and Waters considers that the number 12 has been incorrectly recorded 

 by those authors. The number given for A. viytili is 15 — iS, on Hincks' authority, while 

 Silbermann 3 ) gives 16 — 20. It is difficult to count the retracted tentacles of a Polyzoon seen 

 in frontal view, in an entire preparation ; but in the case of the Torres Straits specimen the 

 zooecia are so transparent that the probable error of my enumeration is not very great. 



As in other cases, there is some irregularity in the size and shape of the zooecia, which 

 are, however, fairly regularly hexagonal. They average about 400 u. in length and 290 <x in 

 breadth. The longest and narrowest measured is 560 by 225 u; and the broadest zooecium is 

 400 by 385 u.. 



It should not be concluded, without further evidence, that the thinness of the zoarium is 

 really characteristic of the Torres Straits form. A. polyoum from European waters is well known 

 to increase in thickness during growth, the central parts of the colony thus acquiring a very 

 different appearance from that of the delicate marginal regions (cf. Silbermann, 1906, p. 268). 



Fam. Flustrellidae Hincks. 

 Flustrellidae Hincks, 1880, ''Hist. Brit. Mar. Pol.", p. 504. 



Elzerina Lamx. 



Eiser ina Lamouroux, 18 16, "Hist. Pol. Cor. Flex.", p. 122. 



1. Elzerina blainvillii Lamx. (PI. III, fig. 2). 



Elzerina blainvillii Lamx, 18 16, t. c, p. 123, PI. II, figs 3 a, 3 B. 

 Elzerina blainvillii Lamx, 1821, "Exp. Méthod.", p. 3, PI. 64, figs 15, 16. 



i) A similar character seems to be indicated in the form from Woods Hole, referred to A.mytili by OSBURN (1912, PI. XXVIII, 

 fig. 74»); and it is also shovvn by Silbermann (1906, PI. XIX, figs 1 — 4) in specimens from the Baltic. 



2) Waters, A. W., 1904, "Bry. Franz-Josef Land" II, J. Linn. Soc, Zool., XXIX, p. 180. 



3) Silbermann, 1906, t. cit., p. 272, PI. XIX, figs 6, 7. 



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