are widespread, either geograplTicaliy or in the depths 

 they tolerate. 



The shells of brachiopods provide easy cues for 

 identification. Those of Lingiila are elongate, oval, 

 suggesting a finger nail, and the two valves of a pair 

 have almost identical dimensions and shape. The stalk 

 emerges between them instead of through a hole in 

 one valve. Lingiilci and Crania both represent the 

 smaller class Inarticulata, in which the shells lack an 

 interlocking hinge mechanism. Both valves are mov- 

 able, and sometimes they are twisted in relation to 

 one another while the animal is feeding. 



Crania lacks a stalk, and is found cemented by the 

 ventral valve of its almost circular shell to rocks along 

 north European coasts and in the West Indies. By 

 contrast, Lingiila and the similar animals of genus 

 Glottidia have a long, slender, flexible stalk, and use 

 it to anchor themselves temporarily at the bottom of 

 vertical, mucus-lined burrows in sand flats below low- 

 tide mark. If the waves wash the sand away, these 

 brachiopods can dig in again. Lingiila has many spe- 

 cies in the Indian and Pacific Oceans. It is one of the 

 commonest lamp shells around Japan. There, and 

 around islands in the South Pacific, they are some- 

 times gathered as shellfish for human consumption. 



Glottidia is found on both coasts of America, from 

 the Carolinas to the Gulf of Mexico and from Cali- 

 fornia to Peru. The shell valves may be 1 inch in 

 length, -/s inch across, with a stalk extending about 

 % inch. 



Most modern brachiopods have limy teeth on each 

 shell valve, serving to lock them in alignment at the 

 liinge on the posterior edge. As such they are mem- 

 bers of class Articulata. They differ also from the in- 

 articulates in that the intestine ends blindly, with no 

 anus, and residual wastes must be discharged as pel- 

 lets through the mouth. The supporting stalk extends 

 through a hole in the ventral shell valve, and custom- 

 arily is used to hold the animal in a horizontal posi- 

 tion like a little bracket from some vertical rock sur- 

 face. 



The hinged lamp shells are identified according to 

 the form of the shell and the degree of development 

 of a symmetrical pair of limy loops inside the smaller 

 valve, serving to support the food-collecting, tentacle- 

 bearing arms (lophophores). The one common bra- 

 chiopod along the New England coast ( Terehratiilina 

 septentrionalis), for example, has a pear-shaped shell 

 about Vi inch long, Vs inch wide, within which the 

 skeletal loops have fused into a single ring resembling 

 a small stirrup with a hole the shape of an inverted 

 heart. This same species is found also on coasts of 

 Norway and Scotland. Others of the same large genus 

 occur from the Antarctic to the Arctic in essentially 

 all oceans. 



In Neothyris lenticularia of New Zealand waters, 

 the support for the tentacle-bearing lophophore has 



become a tremendous loop suggesting the newspaper 

 holder below a metal letterbox, except that the center 

 of the delicate skeleton is fixed by a median, blade- 

 like extension from the region of the shell's hinge 

 teeth. Even more crossbars bolster the lophophore 

 skeleton in Laqiieus californianiis, whose barely 

 ridged and highly convex shells reach a length of 

 2 inches on animals affixed to rocks along the Pa- 

 cific coast of North America. 



Lamp shells of the genus Argyrotheca, from the 

 West Indies and western South Atlantic, are her- 

 maphroditic. Otherwise brachiopods are either male 

 or female. Their eggs and sperms are released into 

 the body cavity and discharged from the excretory 

 tubules (nephridia). 



Most brachiopods retain their eggs within the shell 

 valves until fertilization has been followed by some 

 embryonic development. A few possess special brood 

 pouches, either in the vicinity of the tentacle-bearing 

 lophophore or, as in Argyrotheca, as enlargements of 

 the excretory tubules. 



When the swimming larvae are released, they move 

 slowly through the water, propelled by cilia over at 

 least the anterior lobe of the three-lobed body. A few 

 days later, the larva metamorphoses, sinking to the 

 bottom. Its posterior lobe elongates as the supporting 

 stalk. The middle lobe enlarges to envelop the rest 

 of the body and becomes modified into the two layers 

 of tissue (mantle) secreting the shell valves and the 

 food-gathering lophophore. 



Irregularities in the rate of shell secretion usually 

 provide eccentric rings comparable to those that have 

 been used in estimating the age of clams. Apparently 

 four years is a common life span for a lamp shell. 



Three brachiopods attached to a piece of rock and to 

 each other. Preserved. (P. S. Tice) 



