26 



CARBONIFEROUS ENTOMOSTRACA. 



be recognized among some of the foregoing genera and species. But, knowing how 

 greatly these may have differed one from the other in the arrangement and details of 

 limbs, and believing that tubercle and furrow were not without their meaning in the 

 economy of the living animal, we prefer to seize on them as characteristics in these 

 unknown organisms. 



At the same time, if, besides relative size, the tubercles, and even the dorsal furrows, 

 are the consequences of luxuriant growth, or of age, or of sex, we shall avoid error by 

 giving similar trivial names to the seeming analogues in the three different series 

 (1, smooth ; 2, tubercled ; and 3, tubercled, with furrow), taking care to be guided by the 

 shape and general habit in making specific distinctions. 



We have to add that some of the smaller individuals are tubercled, whilst their 

 smooth analogue is of larger size; for example, PI. Ill, figs. 7 and 10, compared with 

 fig. 11. Hence the tubercles are not the result of mere growth; and the differences in 

 other features should have the more weight. 



There is evidently a great temptation to the condensing palaeontologist to group 

 together the three sections that we have here indicated, seeing that the tubercle is very 

 slightly developed in PI. Ill, fig. 5, that the extremely tuberculate Cypridella Edwardsiana 

 (PI. IV, fig. 4) approximates in shape to the smooth Ci/imdinella Cummingii (PI. II, fig. 23), 

 and that the furrow is almost obsolete in PI. Ill, fig. 12. This last form, too, may be 

 compared with Ctjjmdina Bradyana (PI. II, fig. 13) and PI. IV, fig. 1, with PI. Ill, 

 figs. 9, 18, and 19; but, nevertheless, important differences, as to notch and prow, are 

 evident, besides the presence of tubercles ; and none of the Cypridince nor CyjjrMineUce are 

 really comparable with a Cypridellina except in the case of Cypridellina clausa (PI. II, figs. 

 2 and 3), and even there the notch differs, and the specimens are not good enough for 

 a perfect decision. 



Further, if these proposed ge7ienc distinctions fail, there is but a very narrow basis 

 indeed for the separation of species in this extensive group of empty carapace-valves ; the 

 differences of form being, for the most part, susceptible of a graduated arrangement, 

 which, the tubercles and furrows being ignored, and the high probability of great varia- 

 tion in the soft parts being forgotten, would lead to an exceedingly artificial grouping, of 

 but little use in reality. After all, it would be found necessary to recognize some 

 subordinate divisions of long and short, thin or thick, oval or pyriform individuals, which 

 would have still to stand for types of genera or sub-genera ; and, as we have stated 

 already in alluding to the Cypridinads generally (pages 1 and 2), no saving in nomenclature 

 would be made. 



The following species are arranged according to the development of their lower front 

 margin in projection and depth. C. clausa, Burrovii, and yalea are more or less 

 apiculate, with posterior indentation ; the others appear to have been spined on their 

 rounded ends. 



