234 Prof. P. M. Duncan and Mr. W. P. Sladen on the 



same remark holds good for the species Hemiaster digonuSj 

 d'Archiac. 



III. 



The following description of Hemiaster elongatus, nobis, is 

 taken from the work quoted by Prof. Loven, named ' A 

 Monograph of the Fossil Echiuoidea of Sind, collected by 

 the Geological Survey of India, from the Paleeontologia 

 Indica, series xiv. Fasc. 2. The Ranikot series.' We only 

 refer to those points which bear especially upon the diagnosis. 



On page 79 it is stated as follows : — " The apical system is 

 compact and small, the madreporic body is small, and sepa- 

 rates the posterior ocidar plates, but does not extend into the 

 posterior interradial area ; there are only two generative pores, 

 and they are situated on the tops of truncated cones, separated 

 at their bases hy the granular surface of the madreporic. The 

 cones are at the extremities of a narrow transverse ridge. The 

 right and left aiitero-lateral generative plates (2 and 3) are 

 very small, and they are not perforated by generative pores ; 

 and the postero-lateral plates are the largest and are perfo- 

 rated. There is no posterior generative plate. The ocular 

 plates are well developed, and are placed in hollows, and in- 

 trude on the generative plates. The apical system is slightly 

 behind the centre of the test, is small, and is situated on a 

 narrow transverse keel of the lateral interradia." 



The madreporic body is continuous with plate 2, the right 

 anterior, and is perforated by numerous pores; but as the exten- 

 sion of the pores on to the jdates on either side is only tolerably 

 visible in one specimen, we have a doubt upon this matter. 

 The separation of the posterior oculars Nos. I. and V. by the 

 madreporic body is most decided, and our fig. 9 on plate xix. 

 is quite correct. This body is most certainly not prevented 

 from passing backwards by the costals 1 and 4 of Lov^n : on 

 tlie contrary, it passes between these plates, separating them 

 widely, in a manner perfectly foreign and o])posite to what is 

 seen in Palwostoma and Paloiotrojius. 



The peristome is, as stated in our Monograj:)h, placed very 

 excentrically in front, is small, much the longer transversely^ 

 has a rim, and is round at the sides. It is also mentioned that 

 the lip on the anterior end of the plastron is slightly prolonged 

 downwards. The drawing in pi. xix. fig. 8 shows the pro- 

 jecting posterior lip, and fig. 10 indicates that the posterior 

 lip is on a lower level than the front of the actinal part of the 

 test. As we considered the species to be a Hemiaster, there 

 was no necessity to enlarge upon the very characteristic peri- 

 stome in the specific description ; but in order to place the 



