. The Cambridge natural history. Zoology. 544 ECHINODERMATA ECHINOIDEA spines; they are of the tridactyle, the gemmiform, and the ophi- cephalous types, but they have only two jaws. The ambulacral areas on the upper surface of the test can be distinguished only by the flattened respiratory tube-feet (Fig. 2^2, pod'), which can be seen protruding from between the spines. Below these areas are clearly marked, for in the centre of each. pod Fig. 242.—Aboral view of the "Sand-dollar" (Echinarachnius parma), with its spines, m.^, Madreporite ; pod^ small tube-foot with sucker; pod\ flatte
. The Cambridge natural history. Zoology. 544 ECHINODERMATA ECHINOIDEA spines; they are of the tridactyle, the gemmiform, and the ophi- cephalous types, but they have only two jaws. The ambulacral areas on the upper surface of the test can be distinguished only by the flattened respiratory tube-feet (Fig. 2^2, pod'), which can be seen protruding from between the spines. Below these areas are clearly marked, for in the centre of each. pod Fig. 242.—Aboral view of the "Sand-dollar" (Echinarachnius parma), with its spines, m.^, Madreporite ; pod^ small tube-foot with sucker; pod\ flattened respiratory tube-foot. X1. is a well-marked groove proceeding inwards to the peristome. This groove receives lateral branches on its course which traverse the adjacent interambulacral regions. The purpose of these grooves will be explained later. The interambulacral regions do not reach the peristome, which is entirely surrounded by the ambulacral areas. The ambulacral and interambulacral areas both consist of somewhat large hexagonal plates, except in the region of the respiratory tube-feet. Here the pore-plates are not united with one another. This region in each radius is termed. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Company
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
