176 THALLOPHYTA. [CH. 



In a specimen of Dactylopora cylindracea Lam. from the Paris 

 basin, for which I am indebted to Munier- Chalmas, the tubular 

 thallus measures 4 mm. in diameter ; at the complete end it is 

 closed and bluntly rounded. The wall of the tube is perforated by 

 numerous canals, and contains oval cavities which were no doubt 

 originally occupied by sporangia. The shape of the specimens 

 is similar to that of Diplopora, but the canals and cavities 

 present a characteristic and more complex appearance, when 

 seen in a transverse section of the wall, than in the older genus 

 Diplopora. Glimbel has given a detailed account of this 

 Tertiary genus in his memoir on Die sogenannten Nulliporen^ ; 

 he distinguishes between Dactyloporella and Gyroporella by 

 the existence of cavities in the calcareous wall of the tube in 

 the former genus, and by their absence in the latter. The oval 

 cavities in a Dactyloporella were originally occupied by 

 sporangia; in Diplopora and Gyroporella the sporangia were 

 probably borne externally and on an uncalcified portion of the 

 thallus. 



In addition to the few examples of fossil species described 

 above there are numerous others of considerable interest, which 

 illustrate the great wealth of form among the Tertiary and 

 other representatives of the Verticillate Siphoneae. 



Reference has already been made to Vermiporella as an 

 example of a Silurian genus. Other genera have been described 

 by Stolley from Silurian boulders in the North-German drift 

 under the names Palaeoporella, Dasyporella and Rhabdoporella^; 

 the latter genus is compared with the Triassic Diplopora, and 

 the two preceding with the recent Bornetella. 



Schliiter has transferred a supposed Devonian Foraminiferal 

 genus, Coelotrochium^, to the list of Palaeozoic Siphoneae. 

 Munier-Chalmas regards some of the fossils described by 

 Saporta under the name of Goniolina^, and classed among the 

 inflorescences of pro-angiospermous plants, as examples of Jurassic 

 Siphoneae. The shape and surface-features of some of the 



1 Giimbel (71). Vide also Solms-Laubach (91) p. 39. 



2 Stolley (93). » Schliiter (79). ^ Saporta (91) PI. xxxii. &c. 



