Q PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



KEY TO THE SPECIES AND SUBSPECIES OF THE GENUS SYNALPHEUS. 

 NEOMERIS group. 



(Represented on the American coast only by forms with the meropodites smooth 



and unarmed.) 



o'. ^'entral snpernnmerary prominence of the third, fourth, and fifth dactyls 

 obtuse and scarcely marked. 

 6\ All the api)endages slender. 



c \ Meropodites of the third pair four times as long as wide. 



d\ Antennal spine equaling the carpocerite S. fritzmiiUcri. 



d^ Antennal spine surpassing the carpocerite__/(?. frUzmilUcri vJonciatus. 



c"". Meropodites of the third pair three times as long as wide »S'. nobiJii. 



h'\ All the appendages stocky; meropodite of the third pair only 2.5 times as 



long as wide S. sanlucasi. 



a^ Ventral supernumerary prominence of the third, fourth, and fifth dactyls 

 spinous and very marked. 



b\ Antennary spine equaling the carpocerite S. heinpliiUi. 



&l Antennary spine surpassing the carpocerite; traces of spines on the 

 meropodites of the third pair -S. hetnphiUi hmgicornis. 



PAULSONI group. 



a \ Carpocerite long, arising opposite the sei)aration of the stylocerite from 

 the basjil article of the antennulae ; meropodite of the third pair from 3.5 

 to 5 times as long as wide. 

 & \ Basicerite unarmed above, carpocerite 3.5 times as long as wide. 

 c\ Palmar pnmiinence spinous; angles of the telsim sharp, the inner spines 

 t>f its posterior border 3 times longer than the outer spines. 

 d \ liostrum at most equal to the basal article of the antennulip ; anten- 

 nary spine not surpassing the carpocerite 8. toicnsendi. 



d ^ Rostrum, frontal, and antennal spines more elongate. 



S. townsendi lyroductus. 

 c^. Palmar prominence obtuse; angles of the telson right, the inner spines 



only twice the length of the outer /S'. townsendi brci-isinni.s. 



&". Basicerite with a right and not obtuse superior angle; posterior angles 



of the telson very sharj) aS. toicnsendi incxiraniis. 



h^. Basicerite strongly spinous above; carpocerite ovoid, tliree times as long 

 as wide. 

 c\ Meropodite of the third pair less than four times as long as wide. 

 d \ Dactyl of the third pair about 3.2 times as long as wide at the base. 

 r' \ Carpus of the small cheliped spinous above; spine of the scapho- 



cerite equal to the carpocerite *S'. ajdoceros. 



c^ Carpus of the small clieliped not spinous above; spine of the 



scai)hocerite shorter than the carpocerite 8. apioceros siinjosei. 



d^. Dactyl of the third pair 3.8 times as long as wide; carpocerite very 

 swollen, surpassing the antennule by 1.5 times its distal article; 

 spine of the large claw continuing in a straight line its superior 



border /S. apioccros mayagiiensis. 



c ". Meropodite of the third pair more than four times as long as wide. 



d \ Antennal spine longer than tlie antennule ; rostro-orbital interval 

 acute at base; spine of the large claw preceded by a tubercle. 



8. apioceros leiopcs. 



d ". Antennal spine at most equal to the antennule, rostro-orbital inter- 



. val broad and sinuous at base; spine of the large claw continuing 



the superior border in a straight line 8. apioceros desterroensis. 



