THALLOPHYTES, BKYINAE, 43 



These forms in a fragmentary state may look very like Dactyloporidae, 

 but they differ from them in the absence of the central canal ; they are 

 pointed or flattened conical bodies, sometimes united laterally into bundles 

 and becoming broader and wedge-shaped in front, and are supposed to 

 represent the separate rays of the cap of Acetabularia or Polyphysa. They 

 contain a number of conical cavities opening to the outside, which must 

 have inclosed the zoosporangia formed in the rays. Strange to say, they 

 are completely filled with calcareous matter, which is never the case in 

 recent forms. 



It usually happens that as soon as ever a doubtful group has by a lucky 

 hit found a secure place in the system, attempts are at once made to bring 

 a series of enigmatical forms into connection with it, and this has been done 

 in the present case. How far there is any good ground for these attempts 

 is a question which cannot be minutely considered in this place ; we must 

 wait till we have obtained a broader basis for our knowledge of the fossil 

 Dasycladeae, now that we have ascertained their position. Steinmann 

 proposes to unite with them Coelotrochium Decheni, Schliit. from the 

 Upper Devonian beds of Gerolstein, Cyclocrinus from the Silurian strata, 

 Receptaculites also and its allies, and lastly the Jurassic Goniolina. The 

 latter form has, on the other hand, been quite recently compared by Sa- 

 porta 1 with Williamsonia, and been supposed to be the fructification of a 

 Proangiosperm, an Angiosperm in statu nascendi. Deecke 2 describes the 

 Devonian Sycidium, Sandb. as belonging to Dasycladeae, and Schliiter 3 

 cites a number of other forms which have been taken into consideration. 



The genus Penicillus, Lamk. (Espera, Dene), a form of Chlorosporeae, 

 is known to occupy a doubtful position in the system and to require re- 

 newed examination. The unicellular thallus consists of a tuft of dichoto- 

 mously branched filaments divided by constrictions into ovoid or cylindrical 

 segments, which look like cells but communicate freely with one another. 

 The stout solid cell-membrane becomes calcified except at the places of 

 apparent articulation answering to the constrictions, but the incrustation 

 affects only the outer mucilaginously softened layer of the membrane, as is 

 the case also with Acetabularieae. The filaments of the tuft become caked 

 together below, as the calcification increases, into a thick solid and hard but 

 brittle stem. From the younger portions of the filaments which are not yet 

 caked together the calcareous rind readily breaks away in tubular portions 

 corresponding to the members of the plant, or into fragments of the same ; 

 the substance of the rind is not uniform, but is traversed by round or ir- 

 regularly shaped vacant spaces irregularly disposed and crowded together, 

 and sometimes running into one another. Why calcification was interrupted 



de Saporta (2), p. 248. 2 Deecke (1). 3 Schluter (1). 



