448 SYSTEMATIC PALEOXTOLOGY 



morphology of the individuals is well known and complete identifica- 

 tion is possible from a single skeletal unit. 



Genus DISTEPHANUS St6hr. 



This genus consists of those Cannorhaphida which have a skeleton 

 composed of pileated pieces, which are truncated pyramids with a single 

 girdle of meshes, on the summit of which is a simple apical ring. 



Distephanus crux (Ehrenberg). 

 Plate CXXX, Figs. 1, 2. 



Dictyocha crux Ehreuberg, 1840, Monatsberichte d. k. Akad. d. Wiss. Berlin, p. 207. 

 Dictyocha crux Ehreuberg, 1854, Mikrogeologie, pi. xviii, fig. 56; pi. xx, fig. 46, a, 



b, c ; pi. xxxiii, Nr. xv, fig. 9. 

 Distephanus crux Haeckel, 1887, Chal. Rept., vol. xviii, pt. ii, p. 156S. 



Description. — " D. celluiis quinque in formam quadratam ocello medio 

 instructam conjunctis, angulis spinescentibus. Diam. -gV'"-" Ehrenberg, 

 1840. 



Each pileated piece of the skeleton consists of one square central mesh 

 around which are four lateral pentagonal meshes. There are two parallel 

 quadrilateral rings, which are connected by four beams each of which 

 passes from a corner of the smaller ring to the middle of one side of the 

 larger ring. From the corners of the latter are four spines radiating 

 from a center within the space enclosed by the rings and bars but 

 nearer the larger ring. The larger ring is subsquare, the smaller is 

 oval and its size varies greatly in proportion to the size of the larger 

 ring. The spines are of variable and unequal length. There is no 

 regularity in the distribution of the various sizes. Three of them (and 

 sometimes all) are roughly of the same size, the fourth is usually longer. 



This is one of the most abundant Eadiolaria in the Miocene of 

 Maryland, but does not usually occur abundantly in association with 

 other species. 



Occurrence. — Calvert Formatiox. Popes Creek, Boston Bay, Fair- 

 haven, Claiborne, Cambridge Artesian Well (192 to 335 feet), Cris- 

 field Artesian Well (485 to 500 feet). 



Collections. — Maryland Geological Survey, Johns Hopkins University, 



