CLIMACOGKAPTUS. 



is:; 



-Climacograptus Wilsoni 

 Laipw. 



Climacograptus whose theca; tend to ap- 

 proximate in form to those of a 

 Diplograptus. Specimen shows sicula 

 and development of theca l 1 , etc. 

 Dobb's Linn, Lower Hartfell Shales. 

 Coll. Wood. 



The ventral wall of the theca .shows every degree 

 of sigmoid curvature. In the more typical forms 

 of the genus the upper portion of the ventral wall, 

 when seen in profile, is approximately vertical and 

 free (free edge), the middle portion (impressed 

 edge) curves sharply inwards to form the so-called 

 excavation, while the lower portion (edge of contact) 

 resumes the vertical position and is in contact with 

 the theca next below (see Fig. 116). 



In the less typical species the distal free edge 

 becomes more inclined, the excavation shallower 

 and less abrupt, and the whole ventral wall forms 

 a more flattened curve and points in the direction 

 of Diplograptus (see Fig. 117). 



The apertural margin in Climacograptus is 

 typically horizontal, but it may be introverted 

 and in exceptional cases introtorted. 

 The thecal spines are ventral and mesial in position, as in the Dicranograpti(hu. 

 The Gllmacog rapti may be grouped as follows : 

 I. — Glimacograpti in which the free Type Glimacog. scalaris. 

 edge of the ventral wall is approximately 01. scalaris. 



straight and vertical, and the apertural var. normalis. 



margin horizontal. var. miserabilis. 



Gl. rectangular is. 

 CI. medius. 

 Gl. Tornquisti. 

 Gl. minimus. 

 Gl. brevis. 

 Gl. bicurnis. 



var. tridental us. 

 var. peltifer. 

 Gl. supemus. 

 Gl, Wilsoni. 



var. tubularis. 

 Type Glimacog. <in/i<jiius. 



var. lineatus. 

 var. bursifer. 

 Gl. en in/iil us. 

 Gl. tubuliferus. 

 Gl, latus. 

 Gl. styloideus. 



II. — Glimacograpti in which the free 

 edge is slightly inclined, and the apertural 

 margin is somewhat introverted. 



