512 DR. NEWELL ARBER AND MR. F. W. LAWFIELD ON THE 
unequally spaced. This feature is also seen in the foreign types C. macro- 
discus Weiss *, and C. Germarianus (Goepp.) f. 
In C. undulatus (Pl. 28. fig. 4, Pl. 24. figs. 15, 17) there are numerous 
discontinuous grooves or wrinkles, mostly transversely disposed. 
These are the chief types of surface ornamentation known to us, and they 
appear to be often of considerable taxonomie value. 
With regard to the species in which the external surface of the internode 
appears to be longitudinally ribbed there is little that need be said. The 
ribbing varies considerably in its coarseness. In C. majus (Pl. 28. figs. 5, 7, 
and 9, and especially Pl. 25. fig. 22) it is markedly prominent; in C. verti- 
cillatus (Pl. 24. fig. 18) the striations are also more or less strong and 
salient. 
In the foreign type C. pseudogermarianus $ (ef. Pl. 25. fig. 24) the 
ribbing appears to be less prominent. In C. discifer (fig. 23) the striations 
are very fine and close. 
With regard to the sub-cortical striations, which can generally be recog- 
nised, they are usually fine and sometimes discontinuous ; but in C. britannicus 
they are apparently fairly coarse. 
We have here confined our attention almost entirely to the larger stems 
of Calamites. Smaller leafy branches, however, sometimes occur and have 
been figured by many authors, including Weiss. Some of these show nodal 
diaphragms. So far as our limited experience of the internodes of these 
smalier branches is concerned, they appear to be invariably smooth in 
surface. 
Leaf sears.—In our experienee leaf scars of species of Calamophloios are 
only rarely distinct. In some types, such as C. congentus (PI. 28. fig. 2) and 
C. rugosus (fig. 3), they are totally unknown. They are perhaps clearest in 
C. Goepperti (Pl. 24. fig. 13) and in the foreign types C. maerodiscus $ and 
|. They are also fairly well seen in some specimens of 
C. equisetinus 
C. majus. But we have observed no examples of the latter species in which 
they are as clear as in the Liverpool specimen, deseribed a few years ago by 
Groom and Lewis f. We have, in fact, nothing to add to the account of 
these prints and their variation in shape and size as given by those authors, 
We may, however, remark that, as a rule, the scars are always approximated 
and chain-like in form. 
Branch scars.—The branch scars on the external surfaces of the Calamites 
closely resemble those so well known on pith casts, and so far as we are 
* Weiss (1884) p. 94, pl. 11. fig. 2. 
T Kidston & Jongmans (1915) p. 79, pl. 69. fig. 2. 
| Kidston & Jongmans (1915) pl. 61. § Weiss (1884) p. 94, pl. 11. fig, 9. 
|| Weiss (1885) pl. 1. figs. 1 & 2. 4| Groom & Lewis (1912). 
