1873.] J. Wood-Mason — On a Kern Genus of Landcrabs, 250 



Dana's family names still retained, by the substitution of another maxilli- 

 pedary character for the one originally selected and now proposed to be 

 rejected : Gecarcinus, Pelocarcinus, and Hi/lcBOcarcinus, in fact, agree with 

 one another and differ from all other genera of the family in that the 

 exopodites of their outer foot-jaws are short, without flagella, and. completely 

 concealed from view beneath the second joints. The several genera of 

 Gecarcinidce divided into two graups or subfamilies accordingly as they have 

 the exopodites of their outer foot-jaws provided with a ftagellum and applied 

 to the exteraal margin of the second and third joints so as to be externally 

 visible ; or have them short and rudimentary without flagella, and concealed 

 beneath the second joint ; will then be distributed as follows : 



SUBFAM. I. UCAIN^. 



Genus 1. Uca, Leach. 



„ 2. Gecarci]!^ucus, M.-Edw, 

 „ 3. Caedisoma, Latr. 



SuBFAM. II. aECTARCININ^. 

 Genus 1. Gecaecinus, Latr. 

 „ 2. Pelocaecinus, M,-Udw, 

 „ 3. Htljeocaecinus, Wood-Mas. 



A careful study of all the numerous figures and descriptions of species 

 ofGECAECiNiD^, andjinthecases of the genera Oardisama and Gecarcinucus^ 

 of actual specimens has convinced me that the GECAECiNiNiB further agree with 

 one another in the structure of the epistoma which in them is of great length 

 from before backwards and nearly horizontal, thus differing remarkably 

 from the XJcAiNiE in which it is short and nearly vertical ; this part has in 

 Pelocarcinus been described by Milne-Edwards* as " grand, completement 

 a decouvert et confondu en arriere avec le palais," and it appeared to me to 

 pass insensibly into the endostoma or ' palate' in Hylceocarcinus also until I 

 had removed the thick clothing of coarse hairs that obscured the parts when 

 I found no difficulty in distinguishing tl^m. It is also a notable fact tliat 

 the three most closely-allied species of the former, viz,, Gecarci?iiis rurlcola, 

 JPelocarcinus Lalandei, and Hylceocarcinus Humei, have six rows of stroiig 

 spines to the terminal joints of the walking legs, and I would also draw 

 attention to the shallow yellow scars situated in all three on each side of the 

 eye and on other parts of the carapace — tell-tale marks of their descent from, 

 a common ancestor ! 



HYL.EOCAEcrNUs,t n. gen., Wood-Mason. 

 Proc. As. Soc. Bengal, August 1873, p. 161. 

 * Arch, du Mus., 1855, Vol. vii, PI. xv, fig. 2a. 

 t vXaloSf Sylvester, et KapKLVos, caucer. 

 34 



