224 



Trig^onia margaritacea, Lamarck, luir. bednalli, car. nov. 



PL xxviii., figs. 1, 2, 3. 



Trigonia margaritacea, Lamarck, Ann. du Mus., vol. iv., p. 

 355, pi. Ixvii., fig. 2. T. pectinaia, Lamarck, Anim. S. Vert., 

 1819, vol. vi., p. 63: Encyc. Meth., 1832, vol. iii., p. 1048. 



The shell here referred to was first taken on the Soutli 

 Australian shore, between Glenelg and the Semaphore, by 

 Mr. W. Tc Bednall, about the year 1865, and was catalogued 

 by him in a list of South Australian shells, published (for 

 private circulation only) in 1875, and was noticed in his ex- 

 cellent paper on "Australian Trigonias and their Distribu- 

 tion," in Trans. Roy. Soc. S. Austr., vol. i., 1878, p. 79, under 

 the name of T. margaritacea, Lamarck. He said: — "Its par- 

 ticular habitats in our waters have not yet been discovered, 

 no live specimens having yet been dredged." In vol. ix., pp. 

 101-102, Tate recorded it as having been "dredged in life 

 from 8 fathoms in Encounter Bay (R. H. Pulleine)." A few 

 years later, when I had the pleasure of Mr. BednalFs com- 

 pany on one of my earlier dredging excursions, we discovered 

 it in St. Vincent Gulf, and obtained about 70 specimens, liv- 

 ing and dead, from 15 to 20 fathoms, in Yankalilla Bay. 

 Dredging since then has revealed a considerable range, both 

 in depth and area, as shown by the following details : — It 

 has been taken alive at 10 fathoms, 2 small examples : 12 

 fathoms, 7; 14 fathoms, 3; 15 fathoms, 3 ; 17 fathoms, 15; 

 19 fathoms, 16; 15 to 20 fathoms, about 50; 22 fathoms, 

 18. They have been taken as valves from 9 up to 200 fathoms. 

 They have extended from Wallaroo Bay, at 15 fathoms, 

 throughout Spencer Gulf, through Investigator Strait, in St. 

 Vincent Gulf, as far up as Yankalilla Bay, and through Back- 

 stairs Passage. Beyond this, as far as Beachport, where I 

 have only tested at depths from 49 to 300 fathoms, none 

 but dead specimens have been obtained ; though 1 example, 

 the largest in my cabinet, perfect, and quite recent, and 

 of a white colour, was brought up from 110 fathoms at this 

 most easterly of my stations. Their zone is manifestly from 

 12 to 23 fathoms, only stragglers occurring at less depths, and 

 dead shells at greater depths. 



They are very varied in colour, white, pale yellow, light 

 orange, delicate mauve, pink, "crushed strawiberry," and 

 purple. 



This variety is characterized by its very compressed 

 shape, its narrow ribs, its large, oblong, plate-like spines, 

 broader at their free than at their attached ends, features 

 which are exceedingly constant in the very large series ob- 

 tained. T. lamrucl-ii, var. reficvlnta. Ten. Woods, found off 

 the coast of New South Wales, is regarded by Mr. Hedley 



