260 Rhodora [DECEMBER 
ones. In this character the present specimen is exactly like that fig- 
ured by Johnson. Nordstedt also figures this peculiarity in var. poly- 
mazum but it is in his specimens much less marked. 
* Forma curvispinum forma nov. (Plate 64, fig. 11). Length 
with spines 93 p: without 56: breadth with spines 108 u, with- 
out 50: isthmus 13.5 4. Membrane punctate: the spines at the 
end start straight then curve outward making a decided angle. Pud- 
ding Pond, North Conway, common ! 
* Forma callosum forma nov. (Plate 64, fig. 12). Length with 
spines 84 p, without 58 u: breadth with spines 74 p, without 44 n: 
thickness 25 u: isthmus 13 4. There is a thickened spot at the cen- 
ter of each semicell. Pudding Pond, North Conway, frequent ! 
X. TYLERIANUM West. (X. antilopaeum, var. truncatum Wolle). 
Rochester, ( Wolle, Hastings). 
X. CONTROVERSUM W. &. G. S. West. Length with spines 55-59 
p, Without 36.5-38 u: breadth with spines 52-56 p, without 31 u: 
isthmus 7.6-8 p: thickness 20-21 u. Laconia ( Wests). 
* X. BENGALICUM Turner. (Plate 64, fig. 10). Length with spines 
go p, without 68 u: breadth with spines 108 p, without 62 u: isth- 
mus 22 q: length of spines 20 u. Near the upper end of each semi- 
cell is a row of 15-20 small granules. Squam Lake! New to U. S. 
* X. TETRACENTROTUM Wolle. (Plate 64, figs. 8 & 9.) Length 
37 p: breadth with spines 53-57 m, without 32-34 p: isthmus 9.5 p. 
Intervale! Pudding Pond, North Conway! There is a great vari- 
ation in the number and arrangement of the granules in this species. 
In the specimen from Intervale, fig. 9, there are indications of two 
distal spines one on each semicell. 
ARTHRODESMUS Ehrenb. 
A. CONVERGENS Ehrenb. Length 33-40 p: breadth with spines 
45-50 p, without 34-35 m: isthmus 8 p. Intervale! 
A. QUADRIDENS Wood. Length 35 u: breadth with spines 50 p: 
without 35 4: isthmus 8 y. Pudding Pond, North Conway ! 
A. INcus (Bréb.) Hass. var. *LoNGisPINUs Eichl. & Racib. 
Length with spines 42 p, without 14 p: breadth with spines 38 y, 
without 14 &: isthmus 6.5 p: length of spine 20 u. Pudding Pond, 
North Conway ! 
* Var. vaLipus W. & G. S. West. Length with spines 68-71 y, 
