518 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Genotype. Por/nn proboscidae Waters, 1889. 



Range. Jacksonian Recent. 



This genus is zoarial; no special distinct zooecial function separates it from 

 Haswellia. Nevertheless, it has some important zoarial functions susceptible of 

 giving generic characters; the very constant presence of small dorsal avicularia 

 seems to be a very good character. The recent specimens are extremely rare and 

 it is still not possible to study them in detail. 



SEMIHASWELLIA TRIPORA, new species. 



Plate 66, figs. 24-27. 



Description. The zoarium is free, somewhat compressed, not branched, bear- 

 ing laterally large apophyses quite salient; there are three longitudinal rows of 

 zooecia indicated on the dorsal by as many rows of small round avicularia. The 

 zooecia are small, indistinct; the frontal is a tremocyst with sulci. The peristome 

 is quite salient, perpendicular to the zooecial plane, thin and garnished with two 

 small distal avicularia, almost symmetrical; the peristomice is orbicular. The 

 spiramen is a small pore placed just below the peristome, not salient. 



< hpeO.Oo mm. T 



Measurements. Peristomice ^ , Zooecia. /,2=0.35-0.40 mm. 



[lpe=O.Qo mm. 



Affinities. This species differs from Semihaswellia exilis in its very salient 

 peristome and in its much shorter zooecia, less than 0.50 mm. 



Occurrence. Middle Jacksonian: Near Lenuds Ferry, South Carolina (rare). 



Cotypes.Cat, No. 64167, U.S.N.M. 



SEMIHASWELLIA EXILIS, new species. 



Plate 06, figs. 11-23. 



Description. The zoarium is free, cylindrical, thin, formed of three longitudi- 

 nal rows of zooecia opening on only one side; it often bears laterally some cylindri- 

 cal hollow appendages. The zooecia are indistinct ; the frontal is confused with the 

 zoarial surface ; it is formed of a thick tremocyst with tubules, placed on a perfo- 

 rated olocyst; the dorsal is of the same construction and bears a small round 

 salient avicularium without pivot. The peristome is salient, thin, almost perpen- 

 dicular to the zooecial plane; the peristomice is orbicular. The spiramen is small, 

 not salient, and placed on the median axis of the zooecium immediately below the 

 peristome. 



Measurements. Peristomice], Zooecia. Lz = 0.45-0.50 mm. 



[IpcO.Oo-O.Ot mm. 



Variations. The peristome quite often bears two small avicularia symmetri- 

 cally placed (fig. 15). The sulci (figs. 15, 16) do not always appear with clearness 

 on our fossils (figs. 12, 14) ; these are the very fragile ornaments which fossiliza- 

 tion much attenuates. 



We have made numerous longitudinal sections without ever discovering the 

 ovicell; the 50 specimens observed have shown none of them visible exteriorly as 



