CCELENTERATA — HYDROZOA 



119 



ca. 



fragmentary condition of most of these species. The virgula 

 extends through the entire colony (rhabdosome), even penetrat- 

 ing the sicula. Prob- 

 ably all of the Ax- 

 onophora were at- 

 tached to a float of 

 their own secretion. 

 Examples are Diplo- 

 graptus (p. 113), Cli- 

 macograptus and 

 Monograptus. 



Named from the 

 presence of the vir- 

 gula, from the Greek 

 axon, axis, + pherein, 

 to bear. 



Climacograptus (Fig. 

 43). Ordovician- 



Silurian. 



Hydrotheca^ sharply 

 curved below, the 

 upper edge or aper- 

 ture more or less hori- 

 zontal ; hence thev 

 are widely separated. 

 The colony thus pre- 

 sents a ladder-like 

 appearance (whence 

 the name from the 

 Greek climax, a lad- 

 der). The straight outer margins of the hydrothecae are parallel 

 to the axis of the colony. C. typicalis is very abundant in the 

 Utica (Ordovician) shales of New York State. 



Fig. 42. — Phyllograplus angustifolius Hall, from the 

 Ordovician of New York. A, entire colony ( X 4), 

 showing the earliest cup, the sicula {s.); the opening 

 of the latter is between the two spines. B, trans- 

 verse section through the colony (x 6); ca., common 

 canal with its four longitudinal septa; Ih., the in- 

 dividual cups (thecaO. C, P. ilicif alius Hall (X 8), 

 showing the openings of five cups, in each of which 

 was lodged the soft body of a single individual. 

 (All from Ruedemann ; A and B after Holm.) 



