520 MR. A. W. WATERS ON 



The type of Myriozoiom must, of course, be 21. irtmcahtm, and 

 I am not sure that any other living species can be put in the 

 same genus. It has a large number of tentacles, 26-27, which 

 should lead us to consider carefully whether the species with about 

 16 tentacles belong to the same genus, though we cannot conclude 

 from that alone that they do not. 



Levinsen makes one of the characters of Myriozoidea, " de- 

 pendent avicularia seem always to be present," but in the type 

 J/, truncatum no aviculai-ium has been fovind ; another of his 

 characters of Myriozoutn and Myriozoella is no transverse bar in 

 the avicularium, but Schizoj^o^^ella biturrita H. and what I have 

 called S. tibberosa Rss. and Escharoides occlusa have a distinct bar. 

 In M. truncatum. the ovicell is a very large swelling with the 

 covering wall resembling the zooecial wall. S. crtistacea has a 

 prominent round ovicell with radiating ornamentation, S. bitur- 

 rita H. and S. tuberosa have very large wide raised ovicells. In 

 M. simplex Busk no ovicell is externally apparent, though cal- 

 careous sections reveal a concealed ovicell. In ^S". polymorpha the 

 ovicell is also under the calcareous wall, giving, as a rule, no 

 external sign (see my suppl. 'Challenger' Rep. vol. xxxi. pi. ii. 

 figs. 22, 23). In aS*. biturrita and S. polymorj^ha B. there is an 

 avicularium at each side of the oral aperture, and in M. mario- 

 nensis B., at each side well within the peristome, there is a 

 small avicularium with a mandible rounded at the end. 



Now, in ? Escharoides occlusa there is an avicularium on the 

 lip of the peristome at one side *, the ovicell is but moderately 

 raised, with a few large openings, the avicularia have a bar and 

 there are very large glands, at first paired, but often ultimately 

 uniting to form a large multilobvdar gland. So far as my sections 

 go, namely, aS*. Crustacea, M. coarctum, M. subgracile, and M. trunca- 

 tum, there are no glands in the species considered as Myriozoidea 

 except in E. occlusa, and these are quite different from any others 

 known. Also the general absence of glands indicates that Mj'rio- 

 zoidea of Levinsen are not, as considered by him, closely allied to 

 the Reteporidfe, in which glands are so well developed, and which 

 iisually have a sublabial pore and a lamina to the ovicells, also 

 vibices indicating two distinct layeis. The operculum of E. occlusa 

 is quite different from that of any other sf)ecies placed by Levinsen 

 under Myriozoidea. It has a thick boi'der all round, and near 

 the distal edge are two knobs for the attachment of the muscles. 

 Myriozoum truncatum has a very large operculum of a shape 

 quite different from that of the others mentioned, the proximal 

 portion of the operculum being somewhat triangular with the 

 attachments near to the proximal end. M. subgracile, M. coarctum,, 

 and M. Crustacea have the sides of the moderate-sized operculum 

 nearly straight, with the muscle near the side. Hasimllia 

 australiensis has the muscular attachment near the border of the 



* The position of the avicularium is similar in HJiampJwstomeUa , etc., but we do 

 not yet know the systematic value of this character. 



