XUKTH AME1MCAX MARIA TF.RTIAUY BUYOZOA. 93 



tinoly crenulated. On the dorsal olocyst there are two large distal impiv^imi-. 

 The very large distal septula is double in the primoserial zooecia. There are three 

 septulae to each lateral wall. The interopesial cavities are very small, triangular, 

 and rather constant. 



,, . \ho^Q.-24-0.-2<; mm. . (2=0.32-0.36 mm. 



Measurements. Opcsi&\, Zooecia L - _. 



ltd=0.20-0.22 mm. \7z=0.3Q mm. 



Variations. The young zooecia are the more perfect: their mural rim is thin: 

 the large distal septula and the impressions are quite visible (fig. f>). The other 

 zooecia have a mural rim enlarged at the base (fig. 8). The primoserial zooecia are 

 engendered, following the rule, by a zooecium of larger dimensions (figs. 6. S). 



The origin of the multiplicity of the lamellae is quite remarkable. On the 

 /oarium may be perceived a sort of subcolony, one superimposed upon the other, 

 which does not arise from one fixed larva. When the two distal septulae are not 

 on the same plane (fig. 5), the uppermost septula corresponds to another higher 

 lamella of zooecia covering the normal one and the first of these zooecia is like 

 an ancestrula of the subcolony which comes forth then as a spiral. This disposition 

 is clearly visible on figure .". 



Deformed zooecia are common. They result quite often from the meeting of 

 two subcolonies (figs. 3, 4). Sometimes they appear on the zoarium as zooecia 

 wanting in vigor and incapable of engendering a new zooecium (fig. 3) ; then the 

 two lateral lines are rejoined above them. Their forms are very capricious and 

 escape all analysis. 



The zoarial lamellae are intimately united because of their formation by sub- 

 colonies. Sometimes, however, the lamellae back to back are separable (fig. 7). 

 The dorsal then bears very remarkable, long, prismatic lines on which the zooecia 

 are invisible. 



The lateral walls bear three large septulae. 



Affinities. This species differs from Conopeum ar/m/'ixc, us in its zoarial form 

 and its elliptical opesium. On account of its large zoarial dimensions it is a strik- 

 ing and good guide fossil, and it may l>e determined easily in the field. 



Oci-iirr, in, . Lower .Tacksonian ( Moodys marl) : Various localities about Jack- 

 son, Mississippi (common) : ~2\ miles north of Robert, Mississippi (common). 



Cut, //. Cat. Xo. f>3s7i'. U. S. X. M. 



CONOPEUM ARBORESCENS, new species. 



Plate 20. tins. 10-16. 



Description. The zoaria encrust algae, surrounding them with many superim- 

 posed lamellae, and thus forming t'ree. irregular, ltr<m< lu-d. hollow masses. The 

 zooecia are large, separated by a ridge, elongated, elliptical, or pyriform; the mural 

 rim is flat and very little enlarged at the base. The opesium is oval. The inter- 

 opesial cavities are very small, constant, elliptical, or triangular. 



. [/jo=0.3Ci-u.:; L > mm. , |/.2 = 0.46-0.5u mm. 



.!/, asurerm /</*. Opesia , Zooeciaj, 



(70=0.18 mm. [fe=0.30 mm. 



