DESCRIPTION OF SPECIES 43 



Gonads. The ovary is represented in some zooids by a small group of ova in the upper part of the 

 post-abdomen (oik). The testis consists of a long narrow series of many small pear-shaped follicles 

 occupying much of the length of the post-abdomen (t). No larvae were found. 



Remarks. This species is distinguished from all species of Aplidium described from South America, 

 the Subantarctic, and the Antarctic by the following combination of characters: (1) colony small and 

 loosely attached to a sandy substratum; (2) stomach with twenty to twenty-four folds; (3) post- 

 abdomen conspicuously narrower than abdomen. 



It most resembles three species from New Zealand: A. phortax (Michaelsen, 1924), A. benhami 

 Brewin, 1946, and A. adamsi Brewin, 1946. From these species it is distinguished by characters 

 (1) and (3). 



Distribution. Falkland Islands. 



Aplidium quadrisulcatum sp.n. (fig. 6D, E) 



Holotype. St. 939: size of colony 1 cm. in diameter. 



Diagnosis of species. Colony of variable shape, with sand embedded in the test. Zooids small; 

 oral siphon with six shallow or deep lobes; atrial opening about one-third of the length of the thorax 

 from the base of the oral siphon; atrial languet with 1 median and 2 short lateral lobes; nine to eleven 

 strong longitudinal muscles; 10 rows of stigmata; stomach with four or five indistinct folds. 



Occurrence. ?St. 935 : North Island, New Zealand, 84 m. St. 939: North Island, New Zealand, 

 87 m. 



Colony (Text-fig. 6D). The colonies from St. 939 are small, the largest being 1-3 cm. in diameter. 

 These colonies vary in shape from flat cushion-like masses to single or lobed ovate heads with a 

 narrow stalk. Sand is present on the surface and throughout the common test, rendering the colonies 

 very firm. Systems of zooids are not visible, but a single common cloacal opening is present in each 

 small colony and on each lobe of the larger colonies. A few specimens from St. 935, which probably 

 belong to this species, reach a diameter of 2-3 cm., and completely lack sand. 



Zoom (Text-fig. 6E). The zooid is small, not exceeding 2-0 mm. in length. In most zooids there 

 is no post-abdomen, or a very short one, probably owing to the specimens having been collected out 

 of the breeding season. 



Thorax. The short wide oral siphon is divided into six broad, pointed lobes, and the oval atrial 

 opening (a.o.), is situated opposite the 3rd and 4th rows of stigmata, that is about one-third of the 

 length of the thorax from its anterior end. There is a triangular pointed atrial languet (a.l.) of variable 

 length, with two short pointed lateral lobes near its base. Nine to eleven longitudinal muscles 

 converge on the sides of the abdomen. Ten rows of short stigmata are usually present, with twelve to 

 fifteen in each row. 



Gut. The oesophagus is quite wide, and the squat stomach has four or five rather indistinct longi- 

 tudinal folds. The divisions of the intestine are short. The wide rectum ends in the plain-edged anus 

 opposite the 7th row of stigmata. 



6-2 



