LEPAS PECTIN ATA. 85 



from the common appearance of L. anserifera : this 

 variety is the Pentalasmis dilatata of Leach; and for 

 a long time I considered it as a distinct species. It 

 differs from L. anserifera, in the less thickness of the 

 valves, in their being more finely and yet plainly fur- 

 rowed ; in the greater width of the scuta ; and more 

 especially, of that part of the valve lying between the 

 occludent margin, and the ridge running from the 

 umbo to the apex ; in the less elongation of the area in 

 the terga, bounded by the two occludent margins ; and, 

 lastly, in the less size of the whole individual. The 

 tropin and cirri are absolutely identical. Lately, how- 

 ever, in carefully going over a great suite of specimens, 

 all the above few distinctive characters broke down and 

 insensibly graduated away; and I am convinced that this 

 form is only a variety of L. anserifera ; its different aspect 

 being caused partly by youth, but chiefly, I suspect, from 

 being attached to light objects floating close to the surface 

 of the sea. 



The Lepas anserifera can be distinguished by the 

 slight furrows on its valves from all the other species, 

 excepting L. pectinata: this latter species can be 

 readily known, by the close proximity in the scuta 

 of the occludent margin, and the ridge extending from 

 the umbo to the apex ; by its carina being very narrow 

 above the fork ; by the prongs of the fork diverging 

 at an angle of from 135° to 180°; by the thinness of 

 its valves ; by the coarseness of the furrows on them ; 

 and lastly, by there being at most in L. pectinata only 

 one filamentary appendage beneath the first cirrus. 



4. Lepas pectinata. PL I, fig. 3. 



Lepas pectinata. Spengler. Skrifter Naturhist. Selbskabet, 2, 

 B, 2, H. 5 1793, Tab. X, fig. 2. 

 — muricata (var.) Poll. Test. Utriusque Scicil., vol. i, 

 PL vi, figs. 23, 29, 1795. 



