18 PROCEEDINGS OF THE NATIONAL, MUSEUM vol.67 



hollow; many lamellae curve about a solid branch, as in Leiosoecia 

 proxima. 



In longitudinal section the tubes are cylindrical, with dorsal gem- 

 mation on a basal lamella; they are much recurved at their extrem- 

 ity. The mc-sopores are long, numerous, variable in diameter and 

 length. The exterior lamella has its origin in a tube of an internal 

 lamella; the tubes and the mesopores are very much shorter, but 

 they have the same characters as the tubes of the internal lamella. 



In transverse section the tubes are polygonal, with thin and adja- 

 cent walls. They are much smaller in the vicinity of the basal 

 lamella, which proves that these tubes are club-shaped in their infe- 

 rior part and cylindrical as soon as they are recurved. 



Affinities. — ^This species much resembles Acanthopora pitlchella De 

 Loriol, 1868. According to the figures of this author, the zoarial sur- 

 face presents small very regular tuberosities surrounded by radiating 

 mesopores. We have not had occasion to observe the genotype and 

 we understand little of this particular arrangement. We believe 

 that this is a figure somewhat fanciful of a Multicrescis , with tube- 

 rose visors, like the present species. However, as we are not able to 

 prove this supposition, we will maintain the generic term Ilvlticrescis. 

 If by chance it is identical with De Loriol's species the name of the 

 genus would only be changed and all Multicrescis with visors would 

 then be Acanthopora. 



It is to be noted that the exterior lamella appears to have only a 

 single origin. In the other known Multicrescis there are alway several 

 points of origin. 



Occurrence. — ^Lower Cretaceous (Valangian) : Sainte-Croix (Vaud), 

 Switzerland (common). 



Cotypes. — Cat. No. 69859, U.S.N.M., and Museum Comparative 

 Zoology. 



MULTICRESCIS (ACANTHOPORA) FORMOSA, new species 



Plate 21, figs. 10-12 



Affinities. — Only the figured specimen has been found, and a 

 description is not given, for we have not been able to make thin sec- 

 tions, and on the surface we can not see the difference between the 

 orifice of the tubes and those of the mesopores. 



This species has an aspect very close to Acanthopora pulchella De 

 Loriol, 1868, but the zoarial tuberosities are here triangular visors 

 diversely oriented, so that it is difficult to discover the pores to wliich 

 they correspond. 



The genus Acanthopora D'Orbigny, 1840, differs from Neuropora 

 in that the thickened borders of the peristomes present small conical 

 points in place of the elongated veinules (Haime, 1854). The figures 

 given by Haime and by De Loriol, 1868, indicate clearly that the 



