R. if. Brydone— Chalk Polyzoa. 249 



The species occurs rarely and of small size in the upper subzone 

 of the zone of 0. pilula, and becomes fairly common in the restricted 

 zone of A. quadratus but remains small; at Trimiugham it is 

 abundant and distinctly larger, occasionally attaining a very con- 

 siderable size. I have no specimens from intermediate horizons. 



The avicularia enable it to be distinguished at once from such 

 species as Cellepora VilUersi, D'Orb.,^ -or the earlier figures of Eschara 

 Belarueana, D'Orb.,^ to which zooecially it bears some resemblance. 



Semieschaea occLtrsA, sp. nov. (PI. VIII, Figs. 5-8.) 



Zoarium always adherent. 



Zocecia long and pyriform, with separate side walls ; apertures more 

 or less semicircular, with strongly rounded corners and slightly 

 flattened at the head, by the development of a tiny internal front 

 wall ; imperforate lids which completely seal up the aperture are 

 preserved here and there all over the zoarium and abundantly among 

 the early zooecia. 



Ooecia abundant, narrow helmet-shaped swellings of the foot of the 

 succeeding zooecium. 



Avicularia apparently very similar to those of S. labiatula, but with 

 the infold of the side wall in such low relief that it is very difficult 

 to make out its details (the definiteness of the illustrations has 

 largely accrued in the process of reproduction) ; apertures normally 

 enlarged copies of the zooecial apertures, but with a distinct tendency 

 to rectilinear outlines, which sometimes goes so far as to turn them 

 into rude hexagons ; modified avicularia similar to those of *S. lahiatula, 

 but much less conspicuous, are fairly common. 



The species is common at Trimingham, especially in the lowest 

 beds exposed there, and probably therefore has a further range 

 downwards, and as this range does not extend to the Weybourne 

 horizon it may possibly be of assistance in identifying Chalk 

 intermediate between the Trimingham and "Weybourne horizons. 



Semieschaea Munbesleiensis, mihi.^ (PI. YIII, Pig. 9.) 

 The original figure of this species was inaccurate, and as it is near 

 enough to S. lahiatula for comparison I give a photograph of the type. 

 It will be seen that the avicularia are constructed on the same general 

 plan of infolded side walls as the Lesueuri-tj^e, but cannot be included 

 in the latter, as they are not conspicuously larger than the zooecia. 

 I have found rather primitive specimens of this species very 

 occasionally in the mucronata- chalk of the Isle of Wight and Hants. 



Semieschaea Canui, mihi.^ (PI. YIII, Pigs. 10, 11.) 

 EscHAEA EowEi, mihi.^ (PL YIII, Fig. 12.) 

 I take this opportunity of supplementing the diagrammatic original 

 figures of these species by photographs of specimens lending them- 

 selves to photography more kindly than the types. 



In the case of S. Canui, Fig. 10 shows that this species possessed 

 ooecia in the shape of large, flat, rather inconspicuous swellings, 



1 Pal. Fran?., torn, v, p. 407; pi. 605, figs. 8, 9. 



2 Tom. cit., p. 105, pi. 602, figs. 6-8. 

 2 Geol. Mag., 1906, pp. 289-300. 



