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. lis), 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 they 

 are widely separated. 

 The colony thus pre- 

 sents a ladder-like 

 appearance (whence 

 the name from the 



Fig. 42. — Phyllograpius angustijolius 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; th., the in- 

 dividual cups (theca;). C, P. ilk if 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.) 



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. 



