74 PERCY SLADEN TRUST EXPEDITION 
2. Hydroides norwegica, Gunn (25) 1768; Mérch (87) 1863; Marenzeller (84) 1893; 
Saint-Joseph (45) 1898. 
Specific characteristics: the radii of the operculum form about 22 to 36 rounded 
lobes on the edge of the funnel: in the centre of this is the crown of (14—20) generally 
17 spines with sharp lateral processes. 
Locality. Numerous specimens from the bottoms of SS. Thyra and Silda which were 
dry-docked in Suez after coming through the Canal from Alexandria. This species, 
common in the Mediterranean and English Channel, has not been recorded before from 
the Red Sea and it was no doubt in this case brought from the Mediterranean attached to 
the ships. 
Tubes white and delicate with conspicuous lines of growth, more or less adherent 
but distal end generally erect the whole tube being very much larger than contained 
animals. The length of these is generally about 20 mm. of which the long branchiz and 
thorax together make up about a half; the width varies from 1—2 mm. 
The functional double funnel shaped operculum seems more often to be carried on the 
right the small club-shaped one being on the left, but this is of course subject to reversal 
after loss (Zeleny 51), and both fully developed on their very long pedicles is not an 
uncommon occurrence. ‘The horny transparent spines round the inner funnel have sharp 
lateral processes which appear to collect debris so that the whole top of the operculum is 
frequently hidden by it. The lower funnel of the operculum is colourless and opaque, 
just below it on the slender stem occurs a bright crimson spot. 
The collar is entire and the very large thoracic membrane is colourless and trans- 
parent. The branchize of which there are about 15 pairs are variously “coloured red, 
violet, yellow with white transverse markings or may be colourless” ; there are numerous 
opposite pinnee extending almost to their extremities. 
A full description of this species is given by Saint Joseph (45, pp. 440—443). 
3. Hydroides homoceros, n. sp. (Plate 8, fig. 1). 
Specific characteristics: the opercular funnel has about 17 teeth with lateral 
processes (fig. 1a) and the central crown consists of seven slender spines, each having 
a pair of lateral hooks about half-way up and a median basal internal one. 
Localities. Two specimens from Miladumadulu Atoll and one from Minikoi in 
Prof. Stanley Gardiner’s Maldive Archipelago Collection ; also two from 10—15 fathoms 
off Ras Osowarmembe and four from the bottom of SS. Juba off Zanzibar in Mr Crossland’s 
collection. 
Tube “slightly ribbed, not much bent, mouth simple.” 
The specimens are from 10—20 mm. long without the branchial crown which is 
3—4 mm. high, and composed of 12—17 pairs of gills with only short terminal filaments. 
The inter-branchial membrane is also very short. The spines of the very beautiful 
operculum (fig. 1@) are transparent and yellowish. So also are the teeth with their 
lateral processes into which the margin of the lower funnel is produced. One pair of 
these processes is terminal, the other about half-way down. The pedicle varies in height; 
