OF WESTEEN SIND. 161 



also a swelling along the median line of this area on the actinal surface, which expands 

 towards the margin in the neighbourhood of the periproct. The ornamentation 

 of the interradial and interporiferous areas is uniform and small; it consists of 

 numerous small primary tubercles, indistinctly crenulated, and with a minute perforated 

 mamelon, sunken in deep narrow scrobicules, the intermediate spaces being very 

 narrow, in the narrowest part not more than the width of a single row of granules, and 

 at the wider parts, in the spaces between adjacent scrobicules, always less than the 

 width of the scrobicule. The surface is covered with very minute and not particularly 

 closely crowded miliary granules. The primary tubercles are the most crowded at the 

 ambitus, and become slightly larger and rather more widely spaced on the actinal 

 surface. A well-defined band, devoid of primary tubercles, extends along the median 

 interradial line between the peristome and the periproct. 



The peristome is large, central, sunken in a slight depression of the test, penta- 

 gonal, having the transverse diameter greater than the longitudinal. The ambulacral 

 areas, as before noticed, contract on approaching the peristome, and at a short distance 

 from the extremity are sunken in a depression which increases until it falls into the 

 peristome, where the test is well channelled-out ; in this manner a prominence is given 

 to the otherwise feebly-developed bourrelets. The two anterior bourrelets are broader 

 and more pronounced than the postero-laterals, and the odd posterior one is also 

 broader and somewhat flattened along its margin. The floscelle is only feebly 

 developed, the rudimentary phyllodes being very inconspicuous and represented only 

 by a short line of four or five supplementary pores within each column of ambulacral 

 plates. The pores are rather wide apart ; and the two lines of supplementary pores, 

 present in each ambulacrum, converge slightly as they approach the peristome. Some- 

 times there is a faint outswelling of the poriferous zone just before the extremity, and 

 not unfrequently some irregularity in the serial disposition of the pores, which slightly 

 emphasizes the character of the phyllode. 



The periproct is large, transverse, subelliptical, placed close to the margin, on the 

 rounding which unites the ambitus with the actinal surface and immediately under the 

 posterior rostration. Consequent on this slightly oblique position (in relation to the 

 plane of the actinal surface), the presence of the orifice is just discernible when the 

 posterior part of the test is placed in direct line of view. This aperture has a major 

 diameter of 10 millim. and a minor diameter of 5 millim., in an example 66 millim 

 long ; the major diameter of the peristome being about 7 millim., and the minor little 

 more than 4 millim., in the same specimen. 



Premature form. In young examples, which measure 43 millim. in length, the test 

 is relatively higher, much thicker and more tumid at the margins, and tumid on the 

 actinal surface, the flatter character of the adult form being as yet undeveloped. The 

 peristome is large and subelliptical, without any trace of the pentagonal outline ; and 

 the bourrelets are indicated only by the faintest swelling of the plates in the two anterior 

 interradial areas. The periproct is large, and is situated at a higher level than in the 

 adult, and is quite in the margin. Examples having broad poriferous zones are clearly 

 distinguishable at this age from those with the narrow zones — size and all other 

 characters of the tests being similar. We are unfortunately not in a position to say 



