VENTRICULITES.— SCITIZOEHABDUS. 115 



1870. Cylindfospongia anynstata, Ferd. Roemer^ Geol. Oberschles. p. 309, t. 30. f. 7, 8. 

 1877. Ventriculites angustatus, Quenst. p. p. Petref. Bd. 5, p. 437, t. 136. f. 3, 11, 12, 14. 



Sponges narrow, funnel-shaped or subcylindrical, sometimes with constrictions at 

 intervals. In some examples the aperture at the summit is contracted. The basal 

 end is seldom entire ; the funnel appears to have been supported on a slender cylin- 

 drical stem. The wall appears to be about 4 mm. in thickness. In general the 

 specimens are about 50 mm. in length by 20 in width, but larger forms occur, which, 

 judging from fragments, would measure about 100 mm. long, with a summit-width 

 of 36 mm. 



The outer surface of the wall is reticulate ; the ridges or folds, about 1 mm. wide, 

 are disposed so as to leave circular or somewhat irregular interspaces, from '75 to 

 1 mm. in width, arranged either in quincunx or without definite order. The interior 

 surface of the funnel is not exposed. 



The spicular mesh, as seen in a vertical section of a specimen, is irregular ; the 

 distance between the spicular nodes is '375 mm. 



It is sometimes difficult to separate some of the examples of this species which 

 have the surface-apertures of the wall arranged in quincunx, from specimens of 

 Coscinopora {Ventriculites) quincuncialis, T. Smith, sp. As a rule, however, the 

 canal-apertures in this latter species are much smaller, and the surface is much 

 more even than in V. alcyonoides. In specimens which show the spicular structure 

 the difference is easily ascertainable, for in the type forms of C. quincuncialis the 

 nodes are compact, whilst in the present species they are clearly octahedral. 



The figures of Parkinson and Smith referred to by Mantell must be accepted as 

 representing the type of the species, and not Mantell's description, which embraces 

 more than one species. In the structure of the outer surface of the wall Ventri- 

 culites alcyonoides resembles V. impressics, T. Smith, and it is probable that the 

 disciform examples of Mantell's description belong to this latter species. 



This species appears to be abundant and generally distributed in the Upper Chalk. 



Distribution. Upper Chalk: Wigh ton, Norfolk; Guildford, Surrey; Arundel, Lewes, 

 Sussex ; Boxley, Kent ; Heytesbury, Norton-Bavant, Warminster, Wilts ; Strehlen, 

 Germany (coll. Mantell, W. Smith, T. Smith). 



Genus SCHIZORHABDUS, Zittel, 1877. 



SCHIZOEHABDUS LIBTCUS, Zitt. 

 1877. Schizorhabdus libycus, Zitt. Studien, I Ab. p. 51; Neues Jahrbuch, p. 361. 

 Distribution. Upper Chalk : Libyan Desert {coll. Zitt.). 



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