FALiEOXrOLOGtOAL REPORT OF GEOLOGICAL SURVEY. 471 



foramen which divides these pieces ; the divided sides of the foramen 

 pieces diverge slightly, and join a similar diverging side from an ad- 

 joining foramen piece, with which it unites and forms a ridge, which 

 continues to the margin of the field to which they are joined. The 

 field is diyided longitudinally in the centre, by a deep groove, the fora- 

 men pieces are marked by a slight groove, which crosses them near the 

 centre of their length, and runs the whole length, dividing the field 

 into four bands. Where "the foramen pieees are crossed by this slight 

 groove, they are frequently indented by a furrow, which sometimes con- 

 tinues the whole length of the pieces ; it is frequently neaiiy oblitera- 

 ted, and then presents a rounded, oval, or lozenge shaped dent or hole. 

 These marks have the appearance of the imperfectly closed sides of two 

 pieces having grown together. At one state of their growth they 

 were, probably, in separate pieces. In the best preserved speci- 

 mens the broad faces are seen to be furrowed or grooved transversely ; 

 the ends of these grooves are seen presenting small puncture?, while the 

 sides of the grooves present a double row of little knobs, standing op- 

 posite each other, and joining the two adjacent pieces, which touch 

 each other at these l'idges. The ends of the foramen pieces abutting 

 against the centre furrow of the field, are flattened and rounded, the 

 rounding on the inferior side of the piece being greatest. The flatten- 

 ed ends are ornamented by eight or ten diverging ribs, forming on the 

 ends of the pieces a series of beautiful fan-like ornaments, each slight- 

 ly concave. The foramen pieces number from sixty to seventy to the 

 inch — one specimen having one hnndred and fifty on each side of the 

 field ; another (young,) having only forty-three, or eighty-six in each 

 pseudambulacral space. 



Mouth. The mouth is irregularly rounded, small externally, increas- 

 ing in size a_s the opening passes downward into the body ; it is form- 

 ed of five pieces, lying immediately within the ovarial openings ; it 

 was, doubtless, capable of being opened and largely expanded, by the 

 opening of the five petal-like parts into which the body is divided. 

 There is a deep indentation opposite to, and lying between, the lower' 

 ends of the pseudambulacral fields; this indentation piobably marks 

 the limit of the flexibility of the petals. 



Ovarial openings five, nearly round ; one much larger th ■ i the oth- 

 ers ; the large opening on the point nearly opposite the i aperfeet 



