416 DESCRIPTION OF {^Pohjrjastrica 



PrtfKTTLAKiA cttfUata. — Short, ovate, lanceolate, ventricose at the 

 centre; ends constricted and obtuse ; strife ten in 1 -1200th. Length 

 Ml 50th to l-576th. 



p. dicspTxala. — Linear, elongate, constricted, and obtuse at each 

 end, which consequently appears capitate; striae nineteen in 1 -1200th. 

 Length l-860th to l-480th. Fossil in North and South America, 

 and Sweden. 



P. /«?iceo?a^«5.— Lanceolate, elongate, tapering from the turgid centre 

 to the acute extremities ; both longitudinal and transverse stripes, 

 thirteen of the latter in l-1200th. Length 1-1 150th to l-280th. 



P. viridida. — Straight, lanceolate, slender, one end truncate, the 

 other attenuate and obtuse; strise thii'teen to fifteen in 1-1 200th. 

 Length 1 3000th to l-280th. Alive and fossil. 



P. did/yma. — Striated, rather broad ; viewed from the side, linear ; 

 truncated at both ends, and entire; viewed dorsally, constricted in 

 the middle ; ends sub-orbicular ; it thus ajipears as if formed of two 

 discs joined together. Twenty-three strice in 1-1 200th. Fossil in 

 the chalk marl of Caltanisetta, living in sea water. This species 

 was first observed alive, afterwards fossil, in Sicily. Similar forms 

 are very numerous in the chalk marl of Greece. It is distinguished 

 from P. entomon by the want of the constriction when viewed on the 

 lateral surface; ventral surface with a central colourless stripe. 

 Length 1-1 150th to 1 -480th. (P. 24, f. 12.) 



P. iVbri^^^?cfi?.— Laterally linear, narrow, and truncated at both ends , 

 dorsally broadly ovate, and acute at the extremities ; circumference 

 with a narrowly striated margin, area smooth; thirty strife in 1 -1200th. 

 The N. praetexta, of the Greek chalk marl, is very similar to this 

 species. Length 1 -360th. 



P. quad/rifasciata. — Laterally narrow, linear, truncate; dorsally- 

 broadly ovate, ends acute, margin wide ; a double longitudinal narrow 

 striated band on each half ; hence it is apparently marked by four 

 stripes or bauds, whence the name. Striae twenty in 1- 1200th. 

 Alive in the Baltic. Fossil in the chalk marl of Greece. In the living 

 state it is of a greenish or rusty yellow colour. Length 1 -430th. 



P. cequalis. — Large, lanceolate, oblong, ends constricted, obtuse ; 

 Bides even, miiuilcly piuuate. Iceland. 



