JVew Lower Silurian Bryozoa. 



ARTHOCLEMA CORNUTUM, n. Sp. 



193 



Fig. IS.— Arthroclema cornutum, n. sp. a, four of the primary segments in connec- 

 tion, with three x7, showing the articulating sockets near the base of each, and the 

 usual appearauce of the segments of this series : b, a very perfect primary segment, 

 natural size and xl8, showing unusually deep socket, and the irregular granulations 

 of the surface ; c, a series of six segments of the secondary order, and five of them 

 x7 ; the segments of this order are without articulating sockets, and may have either 

 three or four cycles of zocecia ; d, secondary segment with three cycles of zocecia xl8, 

 showing granose ornamentation and other characters ; e, larger and differently 

 marked secondary segment with four cycles of zocecia xl8; /, transverse section of 

 secondary segment from near its upper extremity, showing five rows of zocecia xl8 ; 

 g, transverse section of primary segment, from near its lower extremity, showing six 

 rows of zocecia xl8. 



Zoarium jointed, the segments consisting, so far as known, of 

 only a primary and a secondary series. Primary segments, six- 

 sided, about 2.2 mm. long, and 0.7 mm. in diameter, with the six 

 angles, more or less sharply defined and produced at the truncated 

 upper extremity into as many horn-like projections. Near the 

 lower extremity, which is often a little bulbous and radially 

 striated, usually two subcircular articulating sockets, placed one 

 on each of two opposite faces of the segment. Zooecia generally in 

 four, rarely in five cycles, the apertures of those of the uppermost 



