258 W. D. Lang — On Stomatopora antiqua. 



V. — On Stomatopora antiqua, Haimb, and its kelated Liassic 



FOBMS. 



By "W. D. Lang, M.A., F.Z.S., F.G.S., of the British Museum (Natural History). 



(WITH A FOLDING TABLE I AND PLATE XIY.) 



f^TOMATOPOBA ANTIQUA was first described and figured by 

 Haime ^ from specimens occurring on Gryplicea in the Lower 

 Lias of France. I have not been able to find any record of an 

 English specimen except that in the Survey memoir on the Lias 

 of England and Wales.- But recently several specimens of a 

 Stomatopora resembling S. antiqua, Haime, were found in the 

 collection of the late Mr. E. F. Tomes. The fact that all the 

 specimens were encrusting Gryphaa is remarkable; for though 

 many hundred specimens of various molluscs from the Lower Lias 

 were searched, and of these all sorts of oysters with especial care, 

 Gryphcea was the only form encrusted by Stomatopora. 



In the British Museum catalogue^ S. antiqua, Haime, is made 

 a synonym of S. dichotoma (Lamouroux),* a Bradfordian form. But 

 an examination of the material alluded to, of which more than 

 a dozen zoaria were sufficiently well preserved to admit of 

 measurements of portions of them after the method described 

 in a former number,^ has shown not only that this form is a distinct 

 species, but that it exhibits features which make it probable that it 

 is more primitive than any other Jurassic Stomatopora as yet 

 described. Even Gi'egory included it with some hesitation in 

 S. dichotoma, for in writing of that species he says ^ : " The one 

 [form] in regard to which I feel most doubt is S. antiqua, Haime, 

 from the Lower Lias. Haime founded this practically only on 

 variations in the branching of the lines of the zooecia. This 

 character is shown by the large series of specimens in the British 

 Museum collection to be of little value. The peristomes are not so 

 much raised as in the typical form, but in this character likewise 

 there are such variations in the same zoarium that the difference 

 is not sufficiently well marked." The systematic value of the two 

 characters mentioned has been discussed in the paper ^ just quoted, 

 in which the author attempts to show that the branching is of 

 paramount importance. 



It seems advisable, having the material in hand, to define the 

 species with greater exactness, revising Haime's definition, and by 

 investigating the stages of growth to gain some idea of its relations 

 to other forms. 



^ J. Haime, " Description des Bryozoaires Fossiles de la formation Jurassique" : 

 Memoires de la Societe Geologique de France, ser. ii, vol. v (1854), pp. 162-163. 

 - H. B. Woodward : "The Lias of England and "Wales," 1893, p. 365. 

 ^ J. "W. Gregory : British Museum Catalogue of Jurassic Bryozoa, 1896, p. 44. 



* J. Lamouroux: "Exposition Methodique des genres de I'ordre des Polypiers," 

 1821, p. 84, pi. Ixxxi, figs. 12-14. 



^ W. D. Lang, "The Jurassic Forms of Stomatopora and Prohoscina" : Gbol. 

 Mag., Dec. V, Vol. I (1904), p. 315. 



* J. W. Gregory: loc. cit., p. 48. 



' W. D. Lang: loc. cit., pp. 318-322. 



