OF TKE MELOSIREiE. 



825 



V.Adriatica (Kiitz.). — Aduate, sessile, 

 of middle size ; yalves convex, nearly 

 hemispherical, very smooth. KB. t. 21. 

 f. 8. Adriatic, (xiii. 33.) Diam. 1-600". 



P. ? prcetexta (E.). — Valves geminate, 

 slightly hispid, neither cellulose nor 

 radiated, but bordered by a raised limb ; 

 middle tiat. KSA. p. 22, Fossil. Greece. 

 Diam. 1-1152". 



P. P wceolaris (E.). — Valves geminate, 

 unequal, urceolate (the one more convex, 

 elongated, the other shorter), each with 

 a plane, raised limb ; cellules none, but 

 about ten smooth rays in the longer, and 

 eiglit apiculate ones in the shorter valve. 

 = Dktyopyxis nrceohiris, EM. pi. 18. f. 3. 

 Fossil. Virginia. Diam. 1-1728". 



P. lo/if/a (E.). — Oblong, two and a 

 lialf times as long as broad, cylindrical, 

 with rounded ends ; suture longitudinal. 

 KSA. p. 22. Fossil. Virginia. L. 1-1080". 



2* Frustules cellulose. Dictyopyxis {E.). 



P. cruciata (E.). — Frustules oblong, 

 with rounded ends ; cellules large, ar- 

 ranged in parallel lines; rim distinct. 

 EM. pi. 18. t". 2.= Coscinodiscus cruciatus, 

 KSA. p. 125. 



/3. HelJe)iica, smaller = DictyopyxisIIel- 

 lenica, EM. pi. 19. f. 13. Fossil. America. 

 Guano, &c. Frequently the disk has 

 some series of its cellules more conspi- 

 cuous and forming a cross. Valves cani- 

 panulate. 



P. Cylindrits (E.). — Cylindrical, witli 

 rounded ends, three times as long as 

 broad ; valves with obscure rows of cel- 

 lules. E:M. pi. 33. 13. f. 8. Fossil. Maiy- 

 land. Diam. 1-9G0". \alves campanu- 

 late, separated by a suture. 



P. Lens (E.).— Frustules laterally de- 

 pressed, lenticidar, cellulose ; valves in 

 front view semielliptic. EM. pi. 18. f. 5. 

 Fossil. Virginia. Diam. 1-G3G". The 

 frustide is oval in the front view, the 

 euture forming the greatest diameter. 



P. areolata (E.). — Valves with a 

 heptagonal, areolate, punctated centre, 

 and seven lateral pmictated areolae. 

 KSA. p. 22. North America. D. 1-960". 



P. gemmifera (E.). — Valves turgid, 

 crystalline, not bordered, furnished with 

 lax series of crystalline nodules, fifteen 

 of which \evj nearly reach the smooth 

 centre. KSA. p. 22. Fossil. Maryland. 

 Diam. 1-792". 



P. compressa (Bail.). — Frustules ellip- 

 tic, bivalve ; valves separated by a plane 

 passing through the longer axis, slightly 

 convex, and with transverse rows of dots. 

 BC. ii. p. 40, f. 13, 14. Florida. 



P. dentata (E.). — Frustides having the 



convex margin furnished with (irregular) 

 slightly prominent little teeth ; cellules 

 rather "large, 6 in 1-1200". KSA. p. 22. 

 Antarctic Ocean. Diam. 1-840". 



P.? Umhata (E.). — Frustules oblong, 

 with a central keel ; valves showing in 

 front a central celkdar surface, and 32 

 to 40 radiating lines; border not cel- 

 lidose. = Steijlianopyxis Umhata, EM. 

 pi. 18. f. 7. Fossil. Maryland. D. 1-792". 

 Ehrenberg's figure is oval, and has a 

 broad, distantly striated, but not cellu- 

 lose rim, and in its centre scattered gi'a- 

 nules. 



P. cristata (E.). — Frustules with gemi- 

 nate, lenticular valves, which are close 

 togetlier, not winged; with a somewhat 

 prominent margin like a thin suture; 

 cellules of disc in vows. ~ Stejjhanojjyxis 

 cristata, EM. pi. 18. f. 6. Fossil. Vir- 

 ginia. Diam. 1-816". Ehrenberg's figure 

 somewhat resembles that of P. Umhata ; 

 but the cellules of the oval valve are 

 crowded, and the striated rim is nar- 

 rower. 



Ohscure or doxihtful Species. 



P. XdyeUi (Ktitz.). — Smooth, one side 

 orbicular, girt with a membranous wing- 

 like ring ; the other side oval, one mar- 

 gin more convex, umbonate in the mid- 

 dle. KSA. p. 889. Switzerland. 



P. Actinocyclus (E.). — Frustules with 

 two flattened, finely cellular and ele- 

 gantly radiated valves; rays 30 to 40, 

 straight and dense. EM. "pi. 18. f. 19. 

 = Cyclotella Actinocyclus, KSA. p. 20. 

 Fossil. America. Diam. 1-720". Ehren- 

 berg figures only the lateral view, which 

 in its radiating series of dots resembles a 

 Coscinodiscus. 



P. Scarahceus (E.). — Oblong, with 

 unequal valves ; when viewed laterally, 

 recalling the figure of the Scarabseus. 

 = Dictyopyxis Scarahceus, E. Fossil. 

 Virginia. Diam. 1-648". CeUides 14 in 

 1-1150". 



P. major (Kiitz.). — Frustules large, 

 elliptic, regLdarly punctated. IvB. t. 1. 

 f. 25. North America ; France. Diam. 

 1-420". Probably a state of P. cruciata, 



P. glohata. — \Ve insert under this 

 name certain spherical bodies of a dia- 

 meter varying from 1-240" to 1-1150", 

 discovered in 1836 by Ehrenberg in 

 fiints near Berlin, and considered by him 

 to belong to the silicious Diatomace^e. 

 Kiitzing has examined these bodies, 

 which occur along with silicious spicida 

 of spono-es and species of Xanthidium 

 and Peridinium, but does not consider 

 them Pyxidiculae. The section of pebble 



