226 MR. J. W. GREGOET ON THE 



Species 1. Notamia wbthbkelli (Busk), 1866. 



Syn. Dittosaria wetherelli, G. Busk^ 1866, Geol. Mag. iii. p. 301 ; G. R. Vine, 1889, Proc. Yorks. 

 Geol. &Polyt. Soc. xi. pp. 158-159, pi. v. fig. 1. 



Records. W. AVhitaker, No. i, p. 594; G. E. Vine, No. i, p. 673. 



Diagnosis. Zoarium in small phytoid tufts ; imperfectly known. Branching 

 dichotomous. 



Zooccia elongate, pyriform. Aperture median and symmetrical, oval, the longer 

 axis in the direction of the length of the zoarium. The aperture opens on the upper 

 border and occupies about a quarter of the front of the zocecium. The surface is 

 ornamented with a double series of areolee ; the innermost series forms an ellipse 

 passing close round the upperside of the aperture and crossing the front wall at about 

 the middle ; the outermost series runs close along the hinder margin. The number 

 varies from 8 to 16 in the inner series, and from 20 to 26 in the outer. 



Bistrihution. London Clay, Highgate (Brit. Mus.). 



Dimensions. The zooecia of the specimen figured measure a trifle over "5 mm. in 

 length. 



Figures. PI. XXIX. figs. 1 a, h. Part of a zoarium, X 37 diam. Brit. Mus. 



Affinities of the Species. This species differs from Notamia loricata (Linn.) in that 

 in the recent species the aperture occupies half the front of the zocecium and is 

 obliquely placed ; it also has no regular series of areola;. The same characters serve to 

 distinguish it from Notamia americana (Lamx.) ^ . A nearer ally is the Notamia prima 

 (Eeuss)-, which differs from it by the smallness of the mouth and the absence of areolae. 



Remarks. This species was founded by Busk on a specimen in the Wetherell Collec- 

 tion which cannot now be recognized, but other specimens labelled by Busk occur and 

 enjoy almost as much authority as the actual figured specimens. Busk made it the 

 type of a new genus, Dittosaria, which has been ignored or overlooked by nearly all 

 subsequent writers. He recognized that it was a close ally of Notamia ( Gemellaria), 

 but distinguished it by its mode of branching; he restricted the old gentis to those 

 which at every fork retain a continuation of the main stem in addition to the two 

 branches. But this is not even a specific character, as is shown by the following- 

 quotation from Mr. Hiacks's [No. 2, p. 20] description of iV^otom'a [G.) loricata: — "The 

 branches are given ofi" from each side of the uppermost pair in a stem close to the top, 

 and at times the stem ascends between them and a triplet is formed in place of the 

 more usual bifurcation." The only other point of difl'erence is that the mouth in this 

 species is not " slightly oblique " as it should be to conform to Mr. Hincks's diagnosis 

 of the genus. But this is hardly of generic value, and Busk certainly regarded the 

 other as the main character. The genus differs from Pasythea, Lamx., by the absence 

 of the two notches at the lower corners of the aperture. 



' Loricaria americana, Lamouroux, No. 2, p. 7, pi. Ixv. fig. 9. 

 " Gemellaria prima, Reuss, No. 7, p. 170, pi. vii. figs. 6, 7. 



