126 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.61. 



Polyascosoecia {Idinonea) lichenoides Goldfuss, 1847. Maa- 



str.ichtian. 

 Polyascosoecia {Idmonea) cancellata Goldfuss, 1827. Cam- 



panian (Danian). 



The last two species, in which the frontal mesopores are replaced 

 by vacuoles, will probably be referred to another genus when the 

 ovicells are better known. 



POLYASCOSOECIA CORONOPUS, new species. 



Plate 20, fig. 1-8. 



Description. — The zoarium is idmoneiform, borne on an expanded 

 base attached to marine objects; the branches are ramified dichoto- 

 mously like the horn of a deer. The linear fascicles are little salient, 

 formed of 5-6 tubes; they are opposite with respect to the median 

 axis of the zoarium and somewhat distant from the latter. The 

 tubes are cylindrical and oriented (longitudinal section). There 

 are mesopores on the anterior face and vacuoles on the posterior 

 face. The ovicell is a large salient sack placed to the right or left 

 of the median axis between three fascicles. 



Width of fascicles 0.10 mm. 



Separation of fascicles .21mm, 



Measurements. — < Diameter of tubes (in section) .12 mm. 



Diameter of basal trunk 1. 50 mm. 



Diameter of branches 1.00 mm. 



Structure. — The general aspect is that of an Idmonea entirely cov- 

 ered with pores on all sides of the zoarium; but the study of thin 

 sections indicates that these pores have not the same structure nor 

 the same function. 



In transverse section all the tubes have not the same diameter, and 

 we can only surmise that the tubes are club shaped. The longitudinal 

 section indicates short cylindrical tubes. This discordance arises 

 from the fact that this section has been made perpendicularly to the 

 zoarial axis and not to the direction of the tubes. A transverse section 

 with unequal tubes crossing from the center to the circumference can 

 therefore reveal, in the Idmoneoid forms, likewise some long, club- 

 shaped tubes as well as short, cylindrical tubes. The necessity of lon- 

 gitudinal sections is therefore absolute. 



In longitudinal section the cylindrical tubes are oriented on the 

 same side of the basal lamella; they grow on the dorsal, one from 

 the other according to the ordinary rule of oriented zooecia. At their 

 extremity they branch into three or four mesopores very regular in 

 their length and their direction. The dorsal is very thick and formed 

 by lamellar tissue similar to that in the Horneridae; it is perforated 

 by vacuoles. These small tubes appear to grow one from the other 



