NEW YORK STATE MUSEUM 



The simple needlelike spurs of the earliest bicornis stage show a 

 tendency to develop wings on their back. In most specimens these wings 

 grow most rapidly at the base of the spines, as in the lines a, b, d, e, f of 

 the plate, whereby in the inward curving varieties a crescent form arises 

 [see 9, 12], in the straight spined forms appendages similar to mackerel- 

 tails [13] and in the recurving forms appendages reminding one of 

 lumbermen's hooks [14]. 



By continued growth of the wings the group of forms is originated, 

 which has been designated as C 1 i m a c o g r a p t u s bicornis var. 

 peltifer [tier II of plate A]. A glance at the plate shows that here 

 again all of the bicornis varieties occur, namely forms with crescent- 

 shaped spines (b), with straight diverging spines (e), straight horizontal 

 spines (g) and recurving spines (f). The oddest looking of these are 

 perhaps those with straight horizontal spines and a triangular shield [19]. 

 Among the peltate forms with crescent-shaped spines two groups become 

 again quite distinct, namely those in which the spines continue to grow and 

 to protrude as needlelike points beyond the wings (as in line d, 16) and 

 those in which the growth of the wings overtakes that of the spines [24]. 



But not in all of the bicornis forms does the wino- grow strongest 

 at the base of the spines, in some it appears first in the middle of the 

 spine as a small outgrowth (as in 5) and continues to grow strongest 

 there and to taper towards both the base and point of the spine (as in 10 

 and 11). These individuals form a distinct group by themselves. By 

 continued growth baglike wings are formed, like those represented in tier 

 III [29 and 30; see also enlargements in text fig. 14, 15]. In this group 

 which I have here designated as var. sisfnum in allusion to the simi- 

 larity of the extreme forms to the standards of Roman legions an inde- 

 pendent outgrowth of two semicircular wings, forming together a disk, is 

 found. This formation is best shown in text figure 14. From its pres- 

 ervation partly below and partly above the other wing it appears that this 

 disk partly overlapped the other older one and had a slightly oblique 

 position, though also growing from the lateral face of the rhabdosome. 



