150 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



horizontal rows, or sometimes both, on the A. and I. plates. 

 Spines large, compared to the size of test, and less numerous 

 than in the other sub-orders. 



Family 1. — Goniocidaridje. Haeckel, 1866. 



Actinal and abactinal system large, and of nearly equal size. 

 Pores composed of single pairs in a narrow vertical zone (ex- 

 cept Diplocidaris — fossil) extending to buccal membrane, A. area 

 narrow with many small plates, I. area wide with few large coronal 

 plates, each surmounted with a single primary perforate tubercle 

 surrounded by a large scrobicular circle. The primary I. spines 

 are large, while those of the actinal system are small flattened 

 papillae, and never ornamented, extending also over the im- 

 bricated buccal membrane. Teeth less complicated than 

 Echinidoe or Diadematidce. Auricles, independent arches 

 originating from the I. spaces. Actinal cuts not in coronal plates, 

 but near the actinosome in the edge of the buccal membrane. 

 Teeth like a gouge ; the jaws have not the large triangular 

 foramen of the Echinidae, nor are the sides of the jaws connected 

 over their central part. 



Genus 1. — Phtllacanthus. Brandt, 1835. 



Test swollen circular, turban shaped, thin, ambulacra almost 

 straight or very slightly undulating. Poriferous zone, broad 

 pairs of pores connected by a slight horizontal furrow. Primary 

 spines variable, cylindrical, triangular, flattened club-shaped, 

 elongate, fluted, or with highly developed lamellae or rows of 

 secondary spines. Tubercles perforate, mammary boss smaller 

 than on Cidaris ; scrobicular circle large, with very prominent 

 granules. Areola deeply sunken. 



This genus must not be confounded with the large " Pencil 

 fish" (Hetrocentrotus mammillatus) so commonly preserved as an 

 ornament, with its long club-shaped spines, brown, tipped with 

 red, and ringed with yellow. In that species it will easily be seen 

 that the test is oblong, and the anal system very small. 



