Description oj Genera and Species. 37 



of the lateral keel more numerous. The spines on the back of the carapace are also 

 less in size and more thickly clustered. The test, too, is quite thin and much 

 wrinkled, the wrinkles winding in and out round the bases of the spines. For this 

 recurring form the varietal name is proposed to distinguish it from the more sturdy 

 parent form with the more formidable spines. 



Locality and horizon. — Same as above. 



Collector.— I). Tait. 



Remarks. — Before leaving the genus Anthrapalcenion it may be as well to (consider, 

 in the first case, the relationship of A. rus.sellianus to the other species of the genus, and 

 afterwards, of the genus to allied forms. To judge of .4. grossarti Salter, as originally 

 figured by hira^ and afterwards by Dr. Henry Woodward,' it bears a close resemblance 

 to A. russellianus, having the same general short flattened form, especially of carapace, 

 with the same serrated lateral keels and antero-lateral spines ; but the serrated ridge 

 keel extending into the long rostrum and interrupted at the cervical fold does not 

 reach the posterior margin, and the fold does not seem to be so pronounced. In the 

 tail, the six segments appear to be like those of the latter species, only there seems to 

 be a difference in the nature and distribution of the ornamentation. The tip of the telson 

 and of the uropods in .1. ijrossarti are broken off, but to judge from the portions left 

 the lateral margins of the telson are smooth, while those oi A. russeUiamis are lobated and 

 serrated. The general form and arrangement of the uropods is much alike in both. 

 There is a strong general resemblance between the carapace of .1. russelianus and that 

 of A. dubius Prestwich [_Apus\ There is a similar denticulated rostrum. The ridge 

 keel, interrupted at the cervical fold, is continued back to the posterior margin, and 

 there are embossed areas set with blunt spines. There are similar serrated marginal 

 keels, but there is not the same pronounced spine at the antero-lateral angles in 

 .4. dubias as in .1. russellianus. 



To judge from the arrangement of the sternal plates and the limbs and tail fan of 

 Pyijocejilialus cooperi Huxley (pi. iv., figs. 8, 9), as figured by hinv' and afterwards by 

 Dr. H. Woodward,^ there is a close relationship between that form and the members of 

 the present geims. There is the same applanated and shortened form, with the body axis 

 very much narrower than the carapace, as shown in all the figures, for there can be no 

 doubt that Huxley was correct in his conjecture expressed in the last paragraph on 



'Quart. Journ. Geol. Soc, 18G1, vol. .xvii., p. .531, lii,'s. 1-4. 

 -Ti-an.'i. Geol. Soc. Glasgow, 1867, vol. ii., \\ 'I'.M. |>1. iii., figs. .5-6. 

 'Quart. Journ. Geol. Soc, 1857, p. .'iO'J, pi. xiii., figs. 1-3. 

 * Trans. Geol. Soc. Glasgow, 1867, vol. ii., pi. iii., figs. 1-2. 



