412 BULLETIN OF THE 



Super-Family ABRANCHIA. 



Genus PROPILIDIUM Forbes & IIanlet. 

 Propilidium ancyloide F. & H. 



Plate XXXI. Figs. 2, 2 b, 2 c. 



P. ancyloide F. & H., II. pp. 443, 444, pi. Ixii. figs. 3, 5; pi. aa, fig. 4, 1850. 



In the publication on deep-water limpets and chitons above referred to 

 (Proc. U. S. Nat. Mus. 1881, p. 402) it was stated that an examination of the 

 available data indicated that Propilidium belonged in the Fissurellidcc, where 

 it might represent an imperforate Puncturella. More lately Dr. Jeffreys sug- 

 gested its identity with Cocculina. 1 have never been able to procure a speci- 

 men of Propilidium with the soft parts preserved in spirits, and all that Dr. 

 Jeffreys could send me for examination was a dried up fragment from a shell 

 collected long since. By soaking this in weak potash solution I was able to 

 restore it sufficiently to determine that the form of the head and tentacles 

 agrees with the drawing of Forbes and Hanley, and that the dentition resem- 

 bles that of PiUdium fulvum, as figured by G. 0. Sars (Moll. Keg. Arct. 

 Norvegise, pi. ii. fig. 12), except that the teeth are more slender and longer, and 

 are somewhat more separated from one another. This shows that the genus 

 belongs in the Docoglossa (in all probability near the Lepetidce), and its stand- 

 ing will depend chiefly upon the character of its branchiae, if it proves to 

 possess them. None could be seen in the soaked specimen, but one could 

 hardly expect any trace of them to remain there, even if originally present. 

 The spiral and sinistral or posteriorly directed nucleus is common to all of the 

 Abranchiata, but in nearly all of them it is lost before the creature attains 

 maturity. In Propilidium with its septum we seem to have the process arrested 

 half-way, the partition remaining unfinished and the nucleus persistent. 



Prof. Verrill has described (Trans. Conn. Acad., VI. p. 205, May, 1884) 

 an American species of this genus, which has until lately rested on its original 

 type, a native of North European seas. P. elegans Verrill was collected off the 

 coast of Virginia in 1,395 fathoms. It has not yet been figured, and in treating 

 of the soft parts Prof. Verrill does not mention the branchise. The animal is 

 blind, like the Lepetidce, and there are no epipodial filaments or fringe. 



The occurrence of P. pertenue Jeffreys is also recorded from the American 

 coast, in 640 fms., by Prof. Verrill, but the genus of the original pertenue is 

 doubtful. 



