CHARACTERISTIC DEEP-SEA TYPES. LAMELLIBRANCHS. 73 



and largest of its genus, white, with a golden epidermis, is pecu- 

 liar in its shape, which resembles that of a small member of the 

 Veneridse. A delicately sculptured Cardium, sometimes painted 

 with bright touches of yellow and scarlet, Cardium perama- 

 bllls (Fig. 304), the most lovely species of the genus from deep 

 water, shares with the little Pecten (Amusium) Pourtalesianum 

 Dall the distinction of bright tints where pallor is the rule. 

 The shell is white, but the spines covering it are orange or 

 crimson. A common and characteristic deep-water form is 

 Limopsis aurita Brocchi, well known as a tertiary fossil in 

 Europe. A small brown Astarte is almost ubi- 

 quitous, ranging in depth from 13 to over 1,600 

 fathoms, and in locality from the tropics to New 

 England. The northern specimens attain many 

 times the size of those from the Antilles. A 

 highly polished rich golden brown Modiola, 

 M. polita V. & S. (Fig. 305), allied to our com- 

 mon mussel, attains a large size in great depths 

 on both sides of the Atlantic. But its shell is 

 very thin ; it spins a large nest of byssal threads, 

 resembling a handful of cotton waste thoroughly 

 drenched with the finest mud, so worthless in 

 appearance that only a biologist would suspect the treasure 

 hidden within. 



The Cetoconcha above mentioned are characterized by gills 



reduced to a mere interrupted 

 line of low lamellae on the ven- 

 tral surface; they are related 

 to Poromya, which has ordinary 

 gills. But there is another 

 group, abundant in deep 

 water, called Cuspidaria, still 

 more remarkable in having ap- 

 parently no gills at all; their 

 shells are provided with a long slender rostrum, like a handle, 

 as shown in C. microrhina Dall (Figs. 306, 307), dredged from 

 continental depths. A striking group, from the beauty of 

 form and sculpture exhibited by its species, is Verticordia, the 



Fig. 305. Modiola 

 polita. |. 



Fig. 306. Cuspidaria microrhina. 



