36 SILICEOUS SPONGES. 



sponges which, in addition to the projecting oscules on the upper surface, are 

 furnished either with pores or oscules on the lower surface of the wall. 



There are very numerous examples of this genus in the Upper Chalk of Flam- 

 borough and in the Middle and Upper Chalk of Germany and Bohemia. They are 

 all similar in their mode of growth, but present distinct specific characters in the 

 dimensions and disposition of the canal-apertures of the upper and lower surfaces of 

 the wall, as well as in the thickness of the wall itself. I have found it a very 

 difficult task to identify any of the Flamborough examples with the figures given by 

 Phillips of the sponges from this locality ; for though there can be little doubt that 

 he has intended to represent one or more species of this genus, the figures given are 

 so imperfect in detail that, in the absence of any description, it is impossible to 

 recognize the species which they are supposed lo indicate. For example, the 

 Sj)on(iia marginata, Phill. Geol. York. pi. i. fig. 5, belongs undoubtedly to the genus 

 Verruculina; but later authors, such as Keuss, Eoemer, and Quenstedt, have each 

 relegated different forms of sponges to Phillips's name, thus clearly showing the 

 insufficiency of his figure to establish the species. A some'vhat similar difficulty 

 exists in respect to some of the species of this genus described by F. A. Eoemer from 

 the North-German Chalk ; for the descriptions are generally so meagre that they 

 would apply to more than one species. 



It is only with reluctance that I have added four new species to the number 

 already included in this genus ; but it seemed preferable to do this, than to place the 

 examples under specific names which have no definite characters assigned to them. 



Verkuculina seeiatopora, Eoemer, sp. (Plate III. fig. 4.) 



1840. Manon seriatoporum, F. A. Roemer, Nordd. Kreide. p. 3, t. 1. f. 6. 

 1878. Verrumdina seriatopora, Zitt. Stud. II Ab. p. 59, t. 4. £. 1. 



There is a fragment of a sponge in the collection which I refer, though not 

 without doubt, to the above species. The wall of the specimen is from 8 to 11 mm. 

 in thickness ; the upper surface is furnished with projecting oscules, 2 mm. in 

 diameter near tlieir bases, partly disposed in linear order. The lower surface appears 

 to be composed of closely interwo\eu fibres; but it is not sufficiently free from the 

 matrix to show if pores are present or not. The spicules of which the fibres of this 

 species are made up are minute irregularly branching bodies with spinous pro- 

 jections on their surfaces. 



Bistnbution. Upper Chalk : Sudmerberg ; Ahlten {ZitteVs coll.). 



Vereuculii^a plicata, Hinde, n. sp. (Plate IV. figs. 2, 2 a, b, c, d.) 



Sponges with plate-like walls, usually incurved, and occasionally, by the meeting' 

 and union of the lateral margins, becoming open funnel-shaped. In a few specimens 

 the walls extend in a horizontal direction, and the sponge is platter-shaped. The 



