66 MR. F, R. C, REED ON THE GENUS LICHAS, [Feb, 1902, 
neck-segment, and three pairs of lateral furrows and a neck-furrow. 
From this archetype all the members of the family may be derived, 
by various classes and degrees of modification proceeding along two 
main lines, 
J.—At avery early period in the initiation of the family, the first 
pair of lateral furrows was prolonged backward in a curved manner, 
so as to meet the second pair of lateral furrows’ at nearly a right- 
angle. Of this stage there has been so far no representative 
discovered, and we may probably regard it as never having been of a 
sufficiently lasting or permanent character to have left represen- 
tatives behind, or to have formed the starting-point of a side-branch 
of the family. Owing to acceleration in the early stages of the 
ontogeny, this stage has not been found in young forms. The 
backward growth of the first lateral furrows seems in fact to 
have continued without cessation, till the third pair of lateral 
furrows was met; and on attaining this level a definite point 
in the phylogeny appears to have been reached, so that from this 
stage important offshoots developed. The growth of the first 
lateral furrows backward was here checked, at least for a time, 
until a strong and numerous group of forms arose possessing the 
essential features of this stage. The union of the first and third 
lateral furrows was complete; and thus there resulted, with the 
help of the axial furrow, the enclosure of the second and third 
lateral lobes of the glabella. 
The second lateral furrows had meanwhile almost or completely 
disappeared, and now but faint and rare traces of their presence are 
found, as before mentioned. The second and third lobes thus became 
completely merged into one lobe on each side, and compose what is 
commonly termed the ‘first’ lateral lobes of the glabella. These 
lobes are thus seen to be bi-composite, and the occasional vestigial 
or reversionary occurrence of the second lateral furrows and the 
outward kink in the course of the prolonged first lateral furrows 
remind us of this fact. 
There are various subsidiary or secondary modifications at this 
stage. 
il The Furrows.—(a) The anterior portions of the first lateral 
furrows may become very faint or disappear (as, for example, in 
Dicranogmus simplex). 
(6) The third lateralfurrows may become weak or obsolete, so that 
the bi-composite lateral lobes are ill-defined posteriorly. This is 
a very common modification, and the extent to which it takes 
place varies even in the same species (as, for example, in Lichas 
celorrhin). The outwardly-bent termination of the first furrow 
usually ends in a deep pit, when the third furrow is relatively weak 
or absent. Examples are Lichas lacuniatus, Metopias Hubneri, and 
1 The new nomenclature of the furrows and lobes, as above explained, is 
employed from this point onward in the present paper. 
