COETNELLA. 179 



a feature to serve for generic distinction ; but the different characters of the spicular 

 structure in the forms referred to these genera afford a more satisfactory basis for 

 separation. Unfortunately, however, this test is inapplicable to the numerous 

 Triassic and Jurassic forms of the genus, the minute structure of which has not, up 

 to the present, been ascertained, and owing to their state of preservation is hardly 

 likely to be known ; but if we accept as the type of the genus a Cretaceous species, 

 Corynella foraminosa, Goldf. sp., we find that the fibres are composed of minute 

 filiform three-rayed spicules disposed generally parallel with each other in the 

 direction of the fibi'e. On the outer surface of the sponge there is an open dermal 

 layer of relatively large three- and four-rayed spicules, but these are only seen in 

 specimens which are very favourably preserved. I have not met with any distinctly 

 simple, uniaxial spicules ; those which at first sight appear to be such, and which 

 Zittel refers to as simple spicules, I have found to be portions of three-rayed spicules, 

 in which the unpaired or basal ray has but a very slight development. 



The inconstancy of the canal-system in sponges of this genus is shown in speci- 

 mens of Corynella foraminosa from the Lower Green Sand at Farringdon. Whilst 

 in some individuals canals are present, in others, precisely similar in all other 

 respects, none are present, or they are restricted to the basal portion of the speci- 

 men where the walls are thickest. Again, in Corynella multidigitata, Mich, sp., no 

 canals are present, but the spicular structure resembles that of typical species of 

 the genus. 



Corynella gracilis, Munst. sp. 



1841. Myrmecium gracile, Miinst. Beitr. ziir Petref. iv. p. 31, t. 1. f. 26, 27. 



1864. Eudea gracilis, Laube, pars, Deuks. d. k. Akad. d. Wiss. Bd. 24, p. 232, t. 1. 



f. 3 a, b. 

 1878. Myrmecium gracile, Quenst. Pctrcf. Bd. 5, p. 526. 

 1878. Corynella gracilis, Zitt. Studien, III Ab. p. 36. 



The fibres of this species, as seen in a transparent section, are from "1 to "14 mm. 

 in thickness ; in places a few wavy lines can be seen in them, but they are too 

 indistinct for their real characters to be determined. 



Distribution. Trias : St. Cassian, Tyrol [coll. Klipstein). 



Corynella pyriformis, Klij)st. sp. 



1843. Cnemidinm pyriforme, Klipst. Beitr. z. g. Kennt. d. dst. Alpcn, p. 291, t. 20. f. 5. 

 1864. Eudea gracilis, Laube, pars, Deuks. d. k. Akad. d. Wiss. Bd. 24, p. 232. 

 1878. Corynella pyriformis, Zitt. Studien, III Ab. p. 36. 



Distribution. Trias: St. Cassian, Tyrol (coll. Klijistein). 



2 A 2 



