| Eighteen smaller spines of nearly equal size and similar form. |  | Two opposite large principal spines (frontal and caudal) equal, | 341. Amphilonche. |
| Caudal spine larger than the frontal spine, | 342. Amphibelone. | ||
| Eight tropical and eight polar spines of different sizes (the latter often rudimentary), | 343. Acantholonche. | ||
| Eighteen smaller spines of nearly equal size and similar form. | ||||
| Two opposite large principal spines (frontal and caudal) equal, | ||||
| 341. Amphilonche. | ||||
| Caudal spine larger than the frontal spine, | ||||
| 342. Amphibelone. | ||||
| Eight tropical and eight polar spines of different sizes (the latter often rudimentary), | ||||
| 343. Acantholonche. | ||||
Genus 341. Amphilonche,[[381]] Haeckel, 1862, Monogr. d. Radiol., p. 389.
Definition.—Amphilonchida with two equal principal spines (frontal and caudal spines not different); the eighteen smaller spines nearly equal.
The genus Amphilonche represents the original and at the same time the most common form of Amphilonchida; the two opposite principal spines are of equal size and form, much larger (and often also of another form) than the eighteen smaller spines; these latter exhibit no marked differences in size and form.
Subgenus 1. Amphiloncharium, Haeckel.
Definition.—Spines in the centre united by triangular faces of their pyramidal bases, propped one upon another. No basal leaf-cross.
1. Amphilonche belonoides, Haeckel.
Amphilonche belonoides, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. xvi. fig. 6, Taf. xviii. fig. 21.
Acanthometra belonoides, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.