46 
GuEviLLE^ on the genus Aiiliscus. 
tlie processes^ widely converging and forming obcordate 
groups ; centrical spaces between the umbilicus and the mar- 
ginal costee^ more or less minutely reticulated. Diameter 
•0032". (Fig. 8.) 
Hab. Patos Island guano^ C. Johnson^ Esq.; E. K. G. 
Surface of the valve much undulated. Processes large^ 
with a broad border. The sets of costse leading to the pro- 
cesses suddenly converging. The space between the umbi- 
licus and the costse of the margin^ extending so as to partially 
enclose the converging sets_, being filled up with a network of 
minutely anastomosing lines. Marginal costse less robust 
than in either of the preceding species. The umbilical space 
is distinctly defined ; but there is no conspicuous quatrefoil. 
Auliscus racemosus, n. sp._, E-alfs, MS. — Valve nearly 
circular_, with definite umbilicus and row of marginal puncta ; 
costse converging to the processes delicate^ terminating in 
little clusters of minute granules on each side of and below 
the processes. Diameter •0024". (Fig. 9.) 
Hab. Barbadoes deposit^ Cambridge estate,, C. Johnson, 
Esq. Communicated by J. Ealfs^ Esq. ; R. K. G. 
An interesting little species^ of which several specimens 
exist. It is not improbable that a larger number of ex- 
amples would show some difference in the amount of the 
punctation ; for there are indications of puncta within the 
marginal circle, and the lateral sets of radiating lines which, 
in the specimens before me, terminately shortly in faint 
granules, may, in other cases, be more fully developed. But 
the character derived from the clusters of granules termi- 
nating the costse, is so distinct and remarkable, as to leave no 
doubt regarding the validity of the species. 
Auliscus reticulatus, n. sp., Grev. — Valve broadly oval, with 
indistinct umbilicus; marginal radiating costse forming a 
rather narrow border, within which the whole area is divided 
into 4 lobes ; the lateral ones very large, and filled with 
a reticulation of anastomosing lines; converging lines also 
often anastomosing. Diameter •OOSS''. (Fig. 10.) 
Hab. Cape of Good Hope, G. M. Browne, Esq. From 
Melobesia, on Haliotis iuberculata, Peru, F. C. S. Roper, 
Esq. 
In the large proportion which the internal 4-lobed space 
bears, to the entire valve this species differs from all the pre- 
ceding, and in the very large comparative size of the lateral 
lobes, it differs most remarkably from its nearest allies, 
certain extreme varieties of A. caelatus. The marginal costse 
form a narrow band, often narrower than in the individual 
represented in the plate ; and the line of separation between 
