gg MODEUN SYSTEM. 



Penseus trisulcatus. Leach, Trans. Linn. Soc. xi. 347. — Supp. to Encyd. 



BrU. i. -121. — Mid. Podop/i. Brit. tab. 42. 

 Inhabits the Welsh Sea. 



Stirps 4. — LrtSrnal antennce inserted below the internal; internal 

 ones with three setae. {External lamella of the tail composed of but 

 one part.) 



Genus 35. PALiEMON. Fair., Latr., Base, Leach. 

 Tow anterior legs didactyle : anterior pair smaller than the second pair : 

 external double palpi with the last joint shorter than the preceding 

 joint. 

 Sp. 1. Val. scrrntus (common Prazon). Rostrum ascending above, with 

 from six to eight teeth, the apex emarginate ; below with from four 

 to six teeth. 

 Astacus serratus. Petin. Brit. Zool. iv. 19. {pi. 16. ftg. 28.) Cancer 

 {Astacus) Squilla. Hcrbst, ii. 55. tab. 27. {Jig. 1.) Palsemon Squilla. 

 Latr. Gen. Crust, et Insect, i. 54. Leach, Edin. Encycl. vii. 401. Pa- 

 la?mon serratus. Leach, Trans. Linn. Soc. xi. 348. — Supp. to Encijcl. 

 Brit. i. 421. — Mai. Podoph. Brit. tab. 43. fig. 1 — 10. 



Variet}' a. Rostrum with six teeth above. 



Subvariety 1. Rostrum beneath with four teeth. 

 2. five teeth. 



Variety /3. Rostrum above with seven teeth. 



Subvariety 1. Rostrum beneath with four teeth. 



2. five teeth. 



3. six teeth. 



"^'ariety y. Rostrum with eight teeth above. 



Subvariety 1. Rostrum beneath with four teeth. 



!2. five teeth. 



3. . ■ six teeth. 



'- Although all the above varieties are common, yet /3 occurs most 

 frequently. In some may be seen the upper edge of the rostrum with 

 ten, the lower with five teeth ; and both edges with but three teeth. 

 The apex is generally notched above, and in t\vo specimens, which 

 may be considered a rare occurrence, the point has been found en- 

 tire. The situation of the teeth on the upper edge is variable, but in 

 most instances the second tooth is at a greater distance from the first 

 than the rest, which are generally equidistant, and rarely extend flir 

 beyond the middle, the rostrum from that part being edentate, with 

 the exception of the emarginate apex." 



Herbst, Latreille, andLeach, formerly considered this species^ 

 as Cancer SijuiUa of Linne ; but Dr. L. has, since the publication of 

 tlie error, met with the true C. Squilla of that author, and has de- 



