212 Mr. n. J. Carter o« a ' 



(fio^. 9, rt^). Colourless, translucent. Surface even, uniformly 

 covered with pores, traversed by longitudinal grooves extend-r 

 ing from the summit to the circumference, indicating the limits 

 of tiie chambers respectively (fig. dd). Aperture at the apex 

 large, ear-shaped or spiral {tig. 9, cc), leading to a vertical colu- 

 mella, around which the cliambers are situated, and into which 

 they ojicu alternately one after another, as they are succes- 

 sively developed on a spirally inclined plane extending from 

 the ixise to the summit of the test. Cliambers sac-shaped, 

 conical, cylindrical or branched, dendriform (fig. 9, b), varying 

 greatly in size, form, and arrangement ; uniformly traversed 

 throughout by large pore-tubes more or less closely apjjroxi- 

 mated (fig. 12) ; chamber smooth within, often presenting om<- 

 sule, on old specimens, a raised network in relief, dividing the 

 surface into an oblique reticulation whose interstices are irre- 

 gular in size and shape. Size about one sixth inch in diame- 

 ter ; aperture about l-60th to l-30th inch in its longest dia- 

 meter. Pore-tube about l-1800th inch in diameter, varying 

 in length witli the thickness of the chamber-wall ; pore itself 

 about l-5400th inch in diameter, or one third of that of the 

 tube. 



JIab. ^Marine. Growing on Tuhipora musica and Siderns- 

 trcea. 



hoc. ? Australia &c. 



Obs. The chief distinguishing character between this and 

 Carjnnteria balanifonnis is the presence of the reticular frame- 

 work in the substance of the shell or chamber-wall of tlie latter, 

 within whose circular interstices the pore-tubes, although ge- 

 neral at first, are subsequently circumscribed (fig. 13, «, h)\ 

 Avhiie in C. monticxdaris tliere is no such framework, and 

 therefore the pores are dispersed generally and uniformly 

 throughout the structure (fig. 12). The oblique reticulation 

 "in relief" appears to be only in old specimens, as before 

 mentioned. It difl:ers from Polytrema iitriculare chiefly in the 

 latter having a separate aperture to each chamber. The genus 

 termed '"'• Dujardinia'''' by Dr. Gray (o^?. et loc, cit.) appears 

 to be a specimen of Carpenteria halaniformis on MytiUcardia 

 variegata with this kind of oblique surface-reticulation, as above 

 mentioned. So, perhaps, when more is known about this in- 

 teresting genus, all these forms, including Polytrema utricidare^ 

 may be found to run into each other inseparably ; for the illus- 

 trations, viz. fig. 9, a, i, given of Carpenteria montictdains are 

 by no means representative of all the specimens that I possess, 

 which for the most part are extremely irregular in form. 



The varieties in which the chambers are branched or den- 

 driform in their outer two thirds (fig. 9, b) very much resemble 



