6 H. H. NEWMAN. 



ties of scute rows in the adjacent pectoral shield, where regularity 

 is rare and irregularity the typical condition. In about three 

 per cent, of individuals the irregular conditions typical for 

 the posterior part of the pectoral shield invade the adjacent 

 parts of the banded region. That this is the correct interpreta- 

 tion of the anomalies in the banded region is evidenced by the 

 fact that out of 84 band anomalies recorded for this study 73 

 occur in the first band, which is contiguous to the pectoral shield. 

 Of the remaining eleven cases 7 occur in band 2, I in band 3 and 

 I in band 8, which is near the other irregular region, viz., the 

 pelvic shield. Irregularities never occur in the middle bands of 

 the carapace, which are farthest from the irregular pectoral and 

 pelvic shields. Another way of interpreting the facts is to look 

 upon the arrangement of scutes in the banded region as due to 

 mechanical adjustments of the primordia of armor elements to 

 flexures during embryonic development. Typically the banding 

 confines itself to the abdominal parts of the armor but occasionally 

 comes in a little farther forward or a little farther back and thus 

 includes parts of the pectoral and pelvic carapace with the 

 typical peculiarities of scute arrangements of these regions. 

 As a result we have these anomalous cases in which the first or 

 second band has the characteristics, doubling, etc., of the 

 pectoral region, and the posterior bands have similarly the char- 

 acteristics of the pelvic region. 



An irregularity in a given band of the banded region may 

 involve as few as two or even one scute. Such an irregularity 

 may consist of a single scute or two in an otherwise double band 

 or a double scute or two in a band otherwise single. The latter 

 situation is much the commonest of all anomalies studied. 

 Sometimes the anomaly manifests itself by a more or less com- 

 plete longitudinal or diagonal splitting of a single acute. Such 

 conditions are to be dealt with separately as there is a consider- 

 able mass of interesting data on the inheritance and distribution 

 of these anomalous double scutes. It is impossible, however, 

 to deal with the inheritance of anomalous band conditions with- 

 out discovering the intimate genetic connection that exists 

 between band and scute anomalies, for sometimes a scute anomaly 

 in a parent reappears as a band anomaly in offspring and vice 

 versa. 



