216 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Measurements . — Opesium of 
zooecia 
Zooecium 
j/m=0.20mm. (measuring only to the poly- 
pidian cony exit 
llo= 0.15 mm. (without the opesiules) 
\L,?=0AQ mm. 
Us =0.30 mm. 
y) 
Opesium of 
onychocellaria 
Onychocellaria 
i hon= 0.20 mm. 
Iopn= 0.10 mm. 
\Lon= 0.40-0.45 mm. 
I Ion— 0.20 mm. 
Variations . — The zooecia with the small opesium (a) are not regularly smaller 
than the others; we can not therefore employ the nomenclature used by Harmer 
for the Steganoporellidae. The reduction of the opesium is due to the enlarge- 
ment of the cryptocyst; we must therefore suppose that the parietal muscles are 
inserted there higher in consequence of the development of an organ of which 
we know nothing. This organ can be neither the ovary , nor the testicles, for we 
have observed ovicells in both forms of zooecia. 
The fusion of the small distal canal of the fusiform onychocellarium with the 
cryptocyst of the distal zooecia is so general that we may now consider its char- 
acter as distinctive upon first examination. The marginal zooecia are unprovided 
with polypidian convexity and lateral opesiules. 
The zoarium sometimes creeps over algae. The unilamellar specimens often 
arise primarily from incrusting specimens which are detached from their sub- 
stratum. 
The mural rim and the cryptocyst are formed of the same elements secreted 
by the endocyst. These elements are grouped in radiating series around the 
opesium (fig. 14). 
Affinities .- — This species differs from Diplopholeos sagittellarium and from 
D. sagittarium by the form of its onychocellarium, by the fusion of .the distal canal 
with the cryptocyst of the distal zooecium, and by its larger zooecial dimensions. 
When the zooecial dimorphism is not apparent, this species much resembles 
Rectonychocella. semiluna; but it is distinguished from it by its incrusting zoarium 
and its very distinct, nearly complete opesiules. 
Occurrence . — Middle Jacksonian (Castle Hayne limestone) : Wilmington, 
North Carolina (common). 
Upper Jacksonian (Ocala limestone) : Old Factory, 1.) miles above Bainbridge, 
Georgia (common) ; Bainbridge, Georgia (very rare) ; 4 miles below Bainbridge, 
Georgia (common) ; 7 miles above Bainbridge, Georgia (common) ; West bank of 
Sepulga Biver, Escambia County, Alabama (common) ; Chipola Biver, east of 
Marianna, Florida (common) ; 9 miles north of Ocala, Florida (common) ; Plant 
System Bailroad wharf at Bainbridge, Georgia (rare). 
Cotypes. — Cat. Nos. 63979, 62582, U.S.N.M. 
