﻿50 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 102 



Very siraiiar to the typical form. All characters lie within the 

 range of variation mentioned for this form, except for some details 

 of the carapace. On the middle and caudal part of its lateral margin 

 there are numerous stout spines considerably larger than those in the 

 principal form, though not so large as the spines at the posterior 

 emargination. All the first-m.entioned spines are directed straight 

 outward. This is a very conspicuous feature and the explanation of 

 the name echinatus. Fm'thermore, the carapace is more roimded and 

 a little larger in relation to the body than in the typical form, and its 

 posterior emargination is less deep, leaving a smaller number (7-10) 

 of rings exposed behind the carapace. 



Remarks. — -It is regrettable that there are not more than 12 speci- 

 mens of this variety, because this small lot cannot be expected to 

 show much of the variation. As a provisional measure I have given 

 it the rank of a variety within L. lynchi, because it shows a great 

 similarity to this species in such important respects as the number of 

 abdominal rings, the characteristic appearance of the eyes and the 

 nuchal organ, and the array of spines on the lateral margins of the 

 carapace. At the same time, there are clear differences between the 

 two forms in the shape of the carapace. 



There is a certain similarity between this variety and L. lem/moni 

 Holmes, especially in the array of lateral spmes on the carapace and, 

 perhaps, also in the position of the nuchal organ. 



But, as I will discuss in more detail later (p. 51), the similarities are 

 more or less uncertain, and I consider L. lemmoin as an insufficiently 

 known species. There are dissimilarities, in any event, among wliich 

 the different shape of the posterior emargination of the carapace is the 

 first to attract attention. I consider it better in this case to estab- 

 lish a new variety than to venture a highly dubious identification with 

 an insufficiently described species. 



LEPIDUnUS LEMMONI Holmes 



Lepidurus lemmoni Holmes, 1894, p. 585 (not Coopey, 1946, p. 338). 



Descri'ption. — The principal points of the description of this insuffi- 

 ciently known species follow: About 4 body-rings exposed behind 

 carapace, 4 or less legless body-rings (the author says 5 instead of 4, 

 but in all probability he counts the telson as a ring). Number of 

 spines on last body-ring never far from 12. Supra-anal plate rather 

 long and may be roimded, truncated (obliquely so in some specimens), 

 or, in some cases, bilobed, mth 2-3 spines in midhne, but no median 

 carina except where the spines are situated. Carapace oval, carina 

 with 10-15 teeth, posterior emargination with 5-7 teeth, sides with 

 numerous small teeth. Nuchal organ round, small, considerably 

 elevated, and located considerably behind the posterior margin of 

 eyes. Length, 28 mm. 



