WITH NOTES ON THE WEST INDIAN SPECIES. 



293 



"Proboscis small, collar large; with no colour, except uniform yellow and fleshy." 

 The pigmented bands were visible in some of the pieces of the abdominal region in 

 the preserved condition. 



Apart from the differences in size and colour-markings there are but few characters 

 which can be definitely stated to establish a specific distinction between the present 

 species and Pt. biminiensis. The impression produced upon the naturalists who collected 

 both species was that they were distinct, and I have thought it would serve the 

 interests of the subject best, under the circumstances, to give them separate names. 

 It is only necessary to remember that Pt. jamaicensis may stand in a similar relation 

 to Pt. biminiensis to that which Pt. robinii (Giard) bears to Pt. clavigera (Delle Chiaje), 

 or Bal. mereschkowskii Nic. Wagner to Bal. kowalevshii Agassiz. 



It is true that there is a striking difference in the matter of the proboscis-pores, 

 but such as it is, it is only due to an exaggeration of the condition observed in 

 Pt. biminiensis. In the present species there are two distinct end-vesicles and two 

 proboscis-pores. At the level of the pores, the vesicles are nearly equal, but the 

 prae-trematic portions of the vesicles are unequal, the bulk of the left exceeding that 

 of the right. Only the left vesicle is in communication with the proboscis coelom ; 

 the right vesicle is blind at both ends. I say at both ends advisedly because in 

 the case of both right and left vesicles, there is a long coecal post-trematic extension, 

 stretching a considerable distance beyond the level of the anterior neuropore, and hence 

 underlying the medullary cord. 



Fia. 5. Transverse section through the proboscis-pores and neuropore of Pt. jamaicensis. 



dv Dorsal vessel (at the point where it passes into the central blood-space and gives off the advehent 

 dermal vessel of proboscis), h Pericardium (solid posterior extremity), ip Left proboscis-pore, rp Right pro- 

 boscis-pore, n The two halves of the neuropore. ph Perihaemal space (anterior extremity), s Stomochord. 

 sW- Skeletal inclusions in the stomochord (due to digitiform processes from the cupule of the uuchal skeleton). 



