53G 



MERISTIC YAIMATIMN. 



[PART i. 



I'm. 193. I. Eight chela of C. pagurus in Coll. Surg. Mus. /,'. ri^-lit index. 

 II. Similar s]>. rimen whose dactylopodite bears x, a supernumerary process. In 

 Coll. Surg. Mus. III. Attacus fluviatilis, left chela bearing .r, a supernumerary 

 process. /,'/, III), right index and dactylopodite. (After LUCAS.) 



both its faces in this plane. There is however no doubt that the 

 tli-tinctidii between these cases and true duplicity is hard to trace 

 and jiuxMbly enough it is not really absolute. 



A.-* each case differs from the others I give a list of those not in private col- 

 lections 1 . The ? indicates that the case perhaps approaches the condition of 

 true duplicity . 



E, ri;i lit. L, left. D, dactylopodite. I, indi'.r. 



El TIEDEMAXN, Meckel's Airli., 1*19, v. p. 127. 



PL u. Jig. 2. 

 JAEGER, G., Jahri-xli. I"-/-, riitrrl. Xatttrk., 



1851, xvn. p. 35, PI. i. fig. 7. 

 id., MeckeVsArch., 1*2(1, p. 95, PL u.n<i. 3. 

 EO'SEL v. EOSENUOF, Ins.-Belust., in. p. 344. 



Jfo. 31. 

 ifiid., fig. 30. 

 LUCAS, ^?i. soc. e(. /";-., 1844, S6r. 2, n. 



p. 45, PL i. t'u). 6. 



FAXON, Han: Hull., vm. p. 259, PL I. fin. 11. 

 //,/., PI. i. fig. 6. 



Kicn \i:n, Ann. .*/. ;/f., 1893, p. 10(J. 

 Co/7. Sur;i. .1/i/s. 

 Co//. Sum. Mu.t. 



Astacus fluvi.it ili* 

 ? A. fluviatilis 



A. fluviatilis 

 A. fluviatilis 



? A. fluviatilis 

 A. fluviatiiis (Fig. 193, in.) 



El 



LD 

 El 



LI 

 LI 



Ilom.irus americanus 

 H. americanus 

 .' Cancer pagurus 

 C. pagurus (l-'i^. I'.tH, i.) 

 C. pagnrus \\'L r . 1 '.::, n.) 



LI 



ED 



I.I 1 



LI 



LD 



(e) Exceptional Cases. 



*82G. Homarus americanus : Right chela. Meropodite sub- 



cyliiiili-ir ;i l instead of fiattoned ; peripherally divides into two 

 ]arts each bearing an articulated appendage as shewn in Fig. li4 

 [The appendage R i> a normal chela. What is R -t- L' ? FAXON, 

 carefully describing the case, thinks that R + L' is a rudimentar\ 

 and reversed ropy of 7i', and that the ease is one of duplicity, 

 lint from the particulars given, and especially from the circum- 

 stance that the carpopodite was "much more spiny' than tin 



-mal. I think it likely that A" + // is morphologically a double 



structure formed of a jtnir of carpopodites compounded together. 



1 \Vitli these may pnli.1]., lie mentioned the following: Apus cancriformis. 

 having upon the K>th foot a second -mall llabelhim shaped like the normal flabellum. 

 The In act was greatly reduced in size. LANKKSTKK, E. E., y.J.M.S., 18S1, xxi. p. 

 350, PI. xx. tig. 12. [In explanation of Plate the abnormal foot is called the 30th.] 



