343 



system was seen as an illuminated diagram of a golden yellow 

 color ; so that in this animal at least, the phosphorescence took 

 place in the substance of the nervous cord. 



The characteristics of this animal are the extraordinary num- 

 ber of the tubes radiating from the central cavity, and its remark- 

 able power of enlarging and contracting. 



The following shells from the United States Exploring 

 Expedition were described by Dr. Gould : — 



Mytilus (Modiola) flabellatus. T. transversa, elongata, 

 trapezoidea, trifariam cuneata ; umbonibus minime terminalibus, 

 acutis, attigentibus ; declivitate umbonali ventricoso, angulato ; 

 marginibus rectilinearibus ; latere postico oblique truncate, baud 

 angulato ; epidermide antice nitido, exusto, postice flavo-viridi, 

 flosculis rigido : intus exalbida. Long. 4 ; alt. If ; lat. 1^ poll. 

 Hob. Puget Sound, Oregon. 



A very well marked species, more than usually cuneate, and 

 with the beaks quite remote from the summit. 



Mytilus (Modiola) areolatus. Testa transversa, ovato-elon- 

 gata, incurvala, tumida ; umbonibus approximatis, angulatis, fere 

 terminalibus; margine dorsali arcuato ; margine ventrali forni- 

 calo, valde hiante ; epidermide nitido, castaneo, portione antico- 

 ventrali sulco limitato : intus alba, limbo dorsali purpurascente. 

 Long. 2 ; alt. \^ ; lat. 1 poll. Hob. New Zealand. 



Somewhat like M. vulgaris ; the beaks are nearly terminal, 

 the byssal opening broader and nearer the beaks, the ventral 

 margin arching inwards instead of outwards at this point ; the 

 epidermis is darker and more shining, and the nacre is different. 



Mytilus (Modiola) hepatigus. T. parva, elongata, ovato- 

 triangularis, antice angustata, ventricosa ; margine dorsali angu- 

 lato; umbonibus acutis, angulatis ; epidermide tenui, livido- 

 corneo, versus fastigium umbonalem flavescente ; intus puni- 

 cea, luteo-marginata. Long. \^ ; alt. f ; lat. f poll. Hah. Fee- 

 jee Islands. 



A small, elongated species, with its dorsal edge obtusely angu- 

 lar, but best distinguished by its peculiar lurid exterior coloring, 

 and its reddish molybdsena-colored interior. 



