266 MR. ARTHUR W. WATERS ON" 



narrow fissure of JR. cellulosa might be developed. In R. elongafa 

 (fig. 9) the lower edge is straighter, with a central tooth, but iu 

 the younger zoceeia (fig. 10) the ovicell has at first a wide circular 

 opening ; nor is this age difference peculiar to this species, for in 

 many cases the opening in the ovicell is larger in the young than in 

 the older ovicells. There are in all very large triangular avicularia 

 on the anterior surface of the zoarium, usually directed alternately. 

 Only in R. Solanderia is there a sublabial pore, very distinct ; 

 while in R. Imperati, which so closely resembles it in most parti- 

 culars, none can be found : thus an important feature of the other 

 groups of Retepora is found in one member of the present group. 

 The mandibles in this group are, so far as I am acquainted 

 with them, all of the same type. They all have a round or oval 

 part much thinner than the rest, which I have called a lucida, 

 and this varies in size and position according to the species. 



Palmicellarta parallelata, sp.nov. (PI. VI. figs. 11-13, 19.) 



Zoarium in one plane, fenestrate, with cylindrical biserial 

 branches, parallel to one another, and joined at more or less 

 regular intervals by barren tubular trabeculse starting from near 

 the distal end of the zooecium. Zooecia cylindrical, distinct ; 

 surface smooth, transparent, vitreous, distal end but slightly 

 raised ; opercular aperture orbicular, operculum thin membranous, 

 no labial pore or fissure ; immediately below the aperture a long 

 rostrum nearly the length of a zooecium with an avicularium near 

 the base directed outwards ; mandible semicircular. Ovicell 

 globose, prominent, slightly elongate and somewhat flattened in 

 front, very finely pitted, with a perforation in the centre of each 

 pit. Dorsal wall similar to the anterior, thin, transparent, smooth, 

 showing the zooecial walls distinctly. The zooecia are placed 

 alternately, and on the dorsal surface at the distal end there is 

 a round raised disk with a round opening in the centre. 



At the side of the branch where the distal and proximal zooecia 

 join there is a round area (PL VI. fig. 13, a), with walls sloping to 

 the junction of the two zooecia, and each of these waRs carries a 

 rosette plate. The trabeculse start from such an area, so that we 

 may say in each zooecium there is the preparation for a trabeculum, 

 though one is only developed to every two or three zooecia. The 

 external lateral wall of the zooecium has a row of small pores. 



The specimen kindly given to me by Professor Parona of Genoa 

 was obtained in Naples, and at first sight was placed with Bete- 

 vora and named R. parallelata. 



