68 Proceedings of the Roifal Irish' Academy. 



others (c). These three types may be regarded as characteristic ; but other 

 forms occur — e.g. irregular forms {d} : double-wheels (e), crosses {g). 



The irregular forms (d) show variations which might be regarded as 

 departures from double-clubs or from the massive spindles, and may be 

 intermediate between the types ^ij and (c;. In the same way those represented 

 by (/) may be looked upon as annectant forms between types {e) and {g). 



The crosses (g) show great variation. 



The following measurements in millimetres may be taken as t}'pical : — 



(a) Spindles, slender and very warty : 0-106 x 0-034 ; 0-10:] x 0-30 ; 



0-09 X 0-03-4. 

 (J) Spindles, very warty and massive: 0-122 x 0-057; 0-118 x 0-057; 



0-114 X 0-049. 

 (c) Double-clubs, with massive warty ends and practically no constriction ; 



0-084 X 0-046; 0-072 x 0-046; 0-08 x 0053. 

 {d} Irregular forms : 0095 x 0-053 ; 0-095 x 0-046 ; 0-076 x 0053. 

 (e) Double-wheels, a few : 0072 x 0-034; 0-057 x 0-027. 

 (/) Crosses: 0-11 x 0076; 0-084 x 0-061; 0-061 x 0-034. 



amended Specific Diagnosis. 



The colony is simple and feebly branched ; in the latter case the branches 

 are long and tlagelliform. The axis is calcareous and brittle ; it is composed 

 of concentric layers ; the surface is marked by longitudinal grooves ; some- 

 times two of these are deeper than the others. The polj'ps are disposed in 

 two longitudinal series ; this arrangement may be obscured in the older parts ; 

 and then the disposition may simulate a spiral. Near the base four rows 

 may occur in each series ; but this number diminishes in the younger parts, 

 so that near the tip there is only a single row, alternately on opposite sides. 

 The verrucae when partially retracted are conical, but when more fully 

 withdrawn are nipple-like. The canal-system is typical. The coenenehyma 

 is moderately thin and finely granular. The spicules are characterized by 

 the presence of large, thick, warty spindles longer than the large double- 

 clubs. 



XYI. Scirpearia hicksoni, n. sp., figs. 28-31. 



It has been found necessary to establish a new species for two portions of 

 what must have been a very long, simple colony ; they are not continuous, 

 however; and judging from tlie difference in the diameter of the axis in the 

 two parts an intermediate piece of considerable length must have been lost. 

 The base is wanting, and this must also have been some distance from the 



