254 ME. J. W. GEEGORT ON THE 



Affinities of the Genus. The British Museum contains a large number of specimens 

 of this species, and these well show its range. One of the smallest specimens, having a 

 zoariuni barely 1 mm. in diameter, is of interest as showing that this genus passes 

 through a Conescharellina [ox Batopora) stage ; the small central zooecium is surrounded 

 by an irregular series of others having the tumid forms, granular walls, and terminal 

 apertures of that genus. This therefore shows that Conescharellina, and especially 

 such a species as C. clithridiata, is a more primitive form than Orhitulipora with its 

 remarkably specialized zoarium. 



The species is also clearly distinct from 0. lenticularis, Reuss [No. ii, p. 289, 

 pi. XXX. figs. 12-14], as to the generic position of which I do not feel able to express an 

 opinion from Reuss's figures. 



Family SMITTID^. 



Genus Muceonella, Hincks, 1880. 

 Diagnosis. Hincks, No. 2, p. 360. 



Species 1. Mucronella angustocecium, n. sp. 

 Syn. Porella concinna,va.r. eoce«a, G. R. Vine, 1891, Proc. Yorks. Geol. & Polyt. Soc. vol. xii. p. 61. 



Diagnosis. Zoarium: unilaminar flat surfaces (1 erect or encrusting algse). 



Zooecia irregular, but with a tendency towai'ds a disposition along radial branching 

 lines. Shape approximately hexagonal. The zocEcia are tumid, rising from a flat 

 surface. Orifice suborbicular : the peristome is high and thickened, especially on the 

 lower margin ; it here bears a small simple mucro. The thick bases of a pair of 

 marginal spines occur on the lower angles of the orifice. The thick lower lip has a 

 distinct median transverse depression. Surface granular. Zooecia separated. About 

 a dozen areolse occur around the lower half of the zooecia. 



Ocecia numerous, granular, globose, but narrow. In one case there are two ocecia to 

 one zooecium. 



Avicularia : none. 



Distrilution. Barton Beds, Barton ; London Clay, Fareham. 



Ty]pe. Brit. Mus. No. 49739. Edwards Coll. From Barton. 



Figures. PL XXXI. fig. 15. Barton Beds. Brit. Mus. No. 49739. Fig. 16. Part of 

 a zoarium from the London Clay, Fareham. 



Affinities. This species reminds one at first sight of the common recent Mucronella 

 ventricosa (Hass.), and it clearly belongs to the same group ; it differs from that species, 

 however, by the small simple mucro, the narrow instead of elongate ocecia, the position 

 of the marginal spines, and in less important points. Probably its nearest ally is 

 M. hornesi (Eeuss) ', of the Middle Oligocene ; the new species, however, may be 

 distinguished by its low instead of elongate ocecia. In this character it most resembles 



^ Lepralia hornesi, Reuss, No. 8, pp. 633, 634, pi. xiii. fig. 5, and No. 7, pp. 173, 174, pi. vii. fig. 12. 



