Measurements. 



702 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Affinities. -This species differs from Filisparsa gracilis in the greater distance 

 of the peristomes (more than 0.70 mm.) and in the presence of multiserial and 

 claviform branches. The young branches are triserial. 



Occurrence. Vicksburgian (Marianna limestone) : Murder Creek, east of 

 Castlebury, Conecuh County, Alabama (rare) ; west bank Conecuh River, Escam- 

 bia County, Alabama (rare). 



Vicksburgian (Red Bluff clay) : Seven and one-half miles southwest from 

 Blaclen Springs, Alabama (rare) . 



Cotypes.Cat. Nos. 65411, 65412, U.S.N.M. 



FIHSPARSA BISERIATA, new species. 



Plate 157, fig. 27. 



Description. The zoarium is formed of thin, rectilinear, biserial branches. 

 The tubes are little distinct, alternate, terminated by a short peristomie ; the peris- 

 tome is thin and orbicular. 



Diameter of the peristome 0.10 mm. 



Distance between the peristomes 0.44 mm. 



Width of the branches 0.24 mm. 



Affinities. This species greatly resembles Crisia. but the zoarium does not 

 appear articulated. D'Orbigny called zoarial forms of -this kind Uniffrisia. The 

 species differs from Filisparsa fallax, which is often biserial, in its smaller peris- 

 tomial diameter (0.10 and not 0.16 mm.). 



Occurrence. Vicksburgian (Marianna limestone) : West bank Conecuh River, 

 Escambia County, Alabama (very rare). 



Holotype.Cnt. No. 65404, U.S.N.M. 



KEY TO THE DETERMINATION OP AMERICAN SPECIES OF THK ONCOL'SOECIIDAE 



Zoarium biserial 



Zoarium pluriserial 3. 



Peristome of 0.10 mm Filisparsa biscriata. 



Peristome of 0.10 mm Filisparsa fallaj-. 



Tubes arranged iu alternate series, branches sinuous Filisparsa liini. 



Tubes arranged in transverse series 4. 



Tubes arranged in quincunx 5. 



Peristome of 0.20 mm Filisparsa typica. 



Peristome of 0.16 mm Filisparsa simulator. 



Peristome of 0.10 mm ^-.Filisparsa alomicula. 



Peristome of 0.20-0.24 mm., large branches,- __. Filisparsa ingens. 



Peristome of 0.24-0.28 mm .-.Oncousoecia varians. 



Peristome of 0.16 nun _ 6. 



Branches always triserial .- 7. 



Branches pluriserial .-8. 



~ \ The peristomes are distant, 1.00 mm_. -.Filisparsa fallax. 



The peristomes are distant from 0.60 to SO mm Filisparsa gracilis. 



Lateral tubes turned toward the dorsal Oncousoecia quinqueseriata. 



Zoarium much compressed with claviform branches Filisparsa laxata. 



