Abstract
This is a comparative study of the morphic features of the carapaces and eggs, made with reference to DADAY'S monograph on living estherids and also a few papers on Asiatic ones by UENO. The length and height of large estherids are about 16 mm. and 11 mm. respectively. This size, when applied to Estherites, is medium. The proportion of length to height is in a range from 1.3 to 1.7 (or at least from 1.2 to 1.8) in most caenestherids and cyzicids but in many leptestherids the range is wider, from 1.4 to 2.2.
The umbo is generally located somewhere in the anterior one-third of the dorsal margin in all of the three groups and notably in the elongated leptestherids it is located very anteriorly. The margin frequently forms an angle with the posterior one in caenestherids and leptestherids while in most cyzicids the junction is not angulated. The arcuate dorsal margin is more commonly met with in the female than in the male.
Except in one tpooth species of Leptestheria, there are various sculptures in the space between the growth-lines which can be classified into four major kinds as follows:
1. punctated ox granulated
2, vertically lined
3. reticulated
4. obliquely lined
The second and fourth kinds are each represented by one form, while the first and third kinds comprise a large variety of sculptures. It is a noteworthy fact that some 25 forms of caenestherids, some 30 of cyzicids and a few of leptestherids have sculptures of the second kind whereas those of the fourth kind are found in 20 forms of leptestherids and 2 of caenestherids. A row of spots or nodes are sometimes met with on the growth line in Caenestheriella but not in any other genus.
Eggs of 36 forms which DADAY illustrated can be classified into eleven groups, but there is no definite relation between these kinds of eggs and generic classification although the educta type of egg is common in Cyzicus.
Thus there are several morphic characteristic of the carapace which are common in a genus or a group of genera but rare in others, or common in female or male. None of these, however, has any absolute value for classification.
