38 Robert E. Coker. 



almost exactly symmetrical, and the second pair of costals are so 

 small at their mesial ends as to be of little significance with refer- 

 ence to the neurals. It may be noted that the second neural is not 

 longer antero-posteriorly than any other scute of the series. (From 

 l^ewmann's Fig. 25.) 



The four next following have an especial interest. 



In I the adjustment appears in the posterior region, but more 

 anteriorly are found two oblique neural elements. The most abnor- 

 mal, ISTo, shows an incomplete seam, which, were it complete to the 

 point X, would be a decided step toward perfecting the adjustment 

 in the manner assumed. (Specimen ]^o. 167, above.) 



II presents a very complicated appearance, but the adjustment is 

 more complete than at first appears. Thus, the two interrupted 

 seams, y and z, are completed by furrows through the areolae. The 

 adjustment would conform perfectly to the usual plan, had these 

 seams been complete, and had there been a seam in the position of 

 the broken line x. The broken lines represent lines of depression of 

 uncertain significance that radiate from the areolae across the rings 

 of growth (cf., the photograph of this carapace, PI. II, Fig. 5). 

 (Specimen ISTo. 210, above.) 



III represents a carapace that is very abnormal on any hypoth- 

 esis. Even here, though, there is found an incomplete seam which 

 makes a step in the direction of the assumed plan of adjustment. 

 (From ISTewTnann's Fig. 7). 



In the carapace represented by IV, the ''law of gTowth" in question 

 would be fully expressed if the incomplete seam were complete to 

 the point x. (From ][Sre^\anann's Fig. 14.) 



Recalling that the growth of the scutes is accomplished by the 

 addition of peripheral rings, and observing that the incomplete seams 

 are in each case in the peripheral or newer part of the scute, one 

 may be justified in making the tentative inference that they indicate 

 post-natal attempts to perfect a previously inadequate adjustment of 

 neurals and costals. Certainly they alter the plan of adjustment, 

 even if it be a coincidence that the alteration in these few cases is 

 in the direction noted. This occurrence of apparently post-natal 

 divisions in cases of imperfect correlation has been observed in 



